Trigonometric Definition and 1000 Threads

  1. anemone

    MHB Evaluate a floor function involving trigonometric functions

    Evaluate \left\lfloor{\tan^4 \frac{3\pi}{7}+\tan^4 \frac{2\pi}{7}+2\left(\tan^2 \frac{3\pi}{7}+\tan^2 \frac{2\pi}{7}\right)}\right\rfloor. Hi MHB, I don't know how to solve the above problem, as I have exhausted all possible methods that I could think of, and I firmly believe there got to be...
  2. anemone

    MHB Solution to Trigonometric System

    Find all reals x,\,y,\,z \in \left[0,\,\frac{\pi}{2}\right] that satisfying the system below: $\sin x \cos y=\sin z\\\cos x \sin y=\cos z$
  3. T

    MHB Integral of trigonometric function

    I have this integral to solve. $$\int_{}^{} (sinx + cos x)^2 \,dx$$ I first start by simplifying the expression: $$\int_{}^{} sin^2x + 2sinxcosx + cos^2x \,dx$$ $$2sinxcosx$$ is $$sin2x$$ (a trigonometric identity) and $$ sin^2x + cos^2x = 1 $$ a trigonometric identity. So, after...
  4. F

    Trigonometric equation for stress

    Homework Statement is the circled part wrong ? Homework EquationsThe Attempt at a Solution how could 0.5 sin2theta = ( 1 + cos2theta ) / 2 ?
  5. anemone

    MHB What is the ratio of sin 5x to sin x in this Trigonometric Challenge?

    Given that \frac{\sin 3x}{\sin x}=\frac{6}{5}, what is the ratio of \frac{\sin 5x}{\sin x}?
  6. H

    I Graphs of inverse trigonometric vs inverse hyperbolic functions

    I noticed the graphs of ##y=\cos^{-1}x## and ##y=\cosh^{-1}x## are similar in the sense that the real part of one is the imaginary part of the other. This is true except when ##x<-1## where the imaginary part of ##y=\cos^{-1}x## is negative but the real part of ##y=\cosh^{-1}x## is positive. I...
  7. 9

    Differentiate trigonometric equation

    Homework Statement a) Differentiate the following equation with respect to: 1) θ 2) Φ 3) ψ (Ua - Ub)' * C * r where: C is a 3 x 3 rotation matrix: [ cos θ cos ψ, -cos Φ sin ψ + sin Φ sin θ cos ψ, sin Φ sin ψ + cos Φ sin θ cos ψ] [ cos θ sin ψ, cos Φ cos ψ + sin Φ sin θ sin...
  8. RoboNerd

    I Question on basic trig substitution with x = sin theta

    Say I have the integral of [ 1 / ( sqrt( 1 - x^2) ] * dx . Now I was told by many people in videos that I substitute x = sin theta, and this has me confused. Wouldn't I need to substitute x = cos theta instead? as x = cos theta on the unit circle instead of sin theta? Thanks in advance for...
  9. anemone

    MHB Can You Prove this Trigonometric Inequality Challenge?

    Let the real $x\in \left(0,\,\dfrac{\pi}{2}\right)$, prove that $\dfrac{\sin^3 x}{5}+\dfrac{\cos^3 x}{12}≥ \dfrac{1}{13}$.
  10. L

    B Simple question about differentiation of trigonometric function

    Explain to me: Why the 2πf came in front? I lost touch and sort of forgot.
  11. R

    B Transform the system of trigonometric equations

    How to extract l and L from the following system of equations:
  12. terryds

    Solving a Trigonometric Limit Problem

    Homework Statement ##\lim_{a\rightarrow b} \frac{tan\ a - tan\ b}{1+(1-\frac{a}{b})\ tan\ a\ tan\ b - \frac{a}{b}}## = ...Homework Equations tan (a - b) = (tan a - tan b)/(1+tan a tan b) The Attempt at a Solution [/B] I don't know how to convert it to the form of tan (a-b) since there are...
  13. Draconifors

    Quick Trigonometric Identity Question

    Hi! I have an integral to solve (that's not the point, though) and the inside of the integral is almost a trig identity: 1. Homework Statement ##sin\frac{(x+y)} {2}*cos\frac{(x-y)} {2} ## Homework Equations I noticed this was very similar to ##sinx+siny = 2sin \frac{(x+y)} {2} *...
  14. D

    Solution to this trigonometric equation

    Homework Statement ##tanx=\frac{(1+tan1)(1+tan2)-2}{(1-tan1)(1-tan2)-2}## find x Homework Equations 3. The Attempt at a Solution [/B] I tried multiplying through the paranthesis and arrived at ##tanx=\frac{(tan1tan2-1)+(tan2+tan1)}{(tan1tan2-1)-(tan2+tan1)}## and i don't know if this is any...
  15. prashant singh

    I Why trigonometric ratios were defined for a unit circle

    To make it useful for any angles. I need a good explanation for this.
  16. V

    What is the proof for 2sin2θ - 1 = sin2θ - cos2θ?

    Homework Statement 2sin2θ - 1 = sin2θ - cos2θ Homework EquationsThe Attempt at a Solution I am unsure of how to prove these. So far all I have is Left side= 2sin2θ - 1 =sin2sin2-1 And I know that right side is equal to 1. But otherwise not sure where to go from there.
  17. P

    Finding sum of roots of trigonometric equation

    Homework Statement Question: Sum of all the solutions of the equation: ##tan^2 (33x) = cos(2x)-1## which lie in the interval ## [0, 314] ## is: (a) 5050 π (b) 4950 π (c) 5151 π (d) none of these The correct answer is: (b) 4950 π Homework Equations ## cos(2x) = 2cos^2(x) -1 ## The Attempt...
  18. anemone

    MHB How do I prove a trigonometric inequality?

    Prove that for all real numbers $x$, we have \left(2^{\sin x}+2^{\cos x}\right)^2\ge2^{2-\sqrt{2}}.
  19. anemone

    MHB How to Prove the Trigonometric Inequality for Real Numbers?

    For real numbers 0\lt x\lt \frac{\pi}{2}, prove that $\cos^2 x \cot x+\sin^2 x \tan x\ge 1$.
  20. A

    Trigonometric equation sin(x) = C*sin(y)

    Homework Statement sin x = C*sin y Find y as a function of x for a given C>0. Homework Equations sin x = C*sin y The Attempt at a Solution This is not actually a problem from a book, but a problem I myself thought about. I was studying elastic collisions in SCM and I obtained 2 equations...
  21. anemone

    MHB Can This Trigonometric Inequality Be Proven for All Real Numbers?

    Prove that \frac{\sin^3 x}{(1+\sin^2 x)^2}+\frac{\cos^3 x}{(1+\cos^2 x)^2}\lt \frac{3\sqrt{3}}{16} holds for all real $x$.
  22. anemone

    MHB How can you maximize a trigonometric expression?

    Maximize $\sin x \cos y+\sin y \cos z+\sin z \cos x$ for all real $x,\,y$ and $z$.
  23. S

    Trying to prove trigonometric integrals on a quarter of circle

    Homework Statement I want to prove that: Homework EquationsThe Attempt at a Solution I tried using the trigonometric identity: sen2x = senx cosx / 2, so, I got: 1/2m∫(sen2x)mdx, x from 0 to pi/2, but now I don't know how to proceed. Can you help me please?
  24. T

    Proving trigonometric identities in a belt and pulley proble

    Homework Statement verify that theta in L = piD + (d-D)theta + 2Csin(theta) is equal to arc-cosine [(D-d)/2C] 2. The attempt at a solution you can see my attempt in the second picture uploaded. i don't think i even got it right
  25. anemone

    MHB Can you factorize this trigonometric expression?

    Factorize $\cos^2 x+\cos^2 2x+\cos^2 3x+\cos 2x+\cos 4x+\cos 6x$.
  26. Greg

    MHB Trigonometric sum with a product as the argument

    Prove $$\sum_{n=0}^N\cos(nx)=\csc\left(\dfrac x2\right)\sin\left(\dfrac{(N+1)x}{2}\right)\cos\left(\dfrac{Nx}{2}\right)$$ I've tried working from the RHS with various identities but haven't managed to come up with anything that works. I suspect this problem involves some trigonometry that I...
  27. Eclair_de_XII

    Can you derive a trigonometric function from its inverse dx?

    Homework Statement Arbitrary derivative of inverse trigonometric function: (sin-1x) = 1/(√1 - x2) Homework Equations f-1(f(x)) = 1/f`(x) The Attempt at a Solution So basically I learned about derivatives of trigonometric functions in class, and I thought maybe this would work: deriving the...
  28. G

    MHB Inverse trigonometric functions

    What's $1. ~ \displaystyle \arccos(\cos\frac{4\pi}{3})?$ Is this correct? The range is $[0, \pi]$ so I need to write $\cos\frac{4\pi}{3}$ as $\cos{t}$ where $t$ is in $[0, \pi]$ $\cos(\frac{4\pi}{3}) = \cos(2\pi-\frac{3\pi}{3}) = \cos(\frac{2\pi}{3}) $ so the answer is $\frac{2\pi}{3}$
  29. H

    Integration of trigonometric function

    Homework Statement I have included the LaTex version of the problem. \int \frac{sin^2 x}{1+cos^2 x} dx Homework Equations Simplifying fraction Partial fractions The Attempt at a Solution I have uploaded my attempt at the solution.
  30. anemone

    MHB Can You Prove $\sin 1+\sin 2+\sin 3+\cdots+\sin n<2$?

    Prove that $\sin 1+\sin 2+\sin 3+\cdots+\sin n<2$.
  31. kaliprasad

    MHB Prove: $(\sin \theta+ i \cos \theta)^8 = \cos 8\theta - i \sin 8\theta$

    Prove that $(\sin \theta+ i \cos \theta)^8 = \cos 8\theta - i \sin 8\theta$
  32. Nono713

    MHB Divergence of a trigonometric series

    Show that this series diverges: $$\sum_{n = 0}^\infty \cos \left ( n^2 \right )$$ (in the sense that it takes arbitrarily large values as $n \to \infty$)
  33. Matejxx1

    Trigonometric equations (finding angles)

    Homework Statement ok so my professor gave me this problem to solve, it goes like this :(I will also have a picture below) In the square (ABCD) is a point P which divides the side BC into 2 halves and point R which divides the side CD into 2 halves The angles at APB and ARB are the same...
  34. A

    Understanding Trigonometric Substitution

    When using trigonometric substitution in calculus you're supposed to always keep in mind the domain of the angle. In the case of √(x2-a2) (where "a" is a number >0) you use x=a⋅arcsec Θ for the substitution. For trigonometric substitution, textbooks state that the domain of Θ must be...
  35. Taryn1

    MHB Write a trigonometric expression as an algebraic expression

    This problem probably should be easy, but I don't remember learning the basic way to do these problems: Write the trigonometric expression as an algebraic expression: cos(arccos x + arcsin x) The answer is zero, but I don't know how to get there...
  36. anemone

    MHB Is This Trigonometric Identity Valid for All Values?

    Let $\dfrac{\cos^4 a}{x}+\dfrac{\sin^4 a}{y}=\dfrac{1}{x+y}$ for all real $a,\,b,\,x,\,y$. Prove that $\dfrac{\cos^8 a}{x^3}+\dfrac{\sin^8 a}{y^3}=\dfrac{1}{(x+y)^3}$
  37. Sollicitans

    Linear Independence of trigonometric functions

    Homework Statement There's no reason to give you the problem from scratch. I just want to show that 5 trigonometric functions are linearly independent to prove what the problem wants. These 5 functions are sin2xcos2x. sin2x, cos2x, sin2x and cos2x. Homework Equations...
  38. D

    Trigonometric Problem: Solving for sin(x/2)*cos(5p/4) with Given Conditions

    Homework Statement cos(x - 3p/2) = - 4/5 p <x< p/2 sin(x/2)*cos(5p/4)= ? Homework Equations The Attempt at a Solution I made it as far as to determine that sinx= 4/5 and cosx = - 3/5 but can't seems to progress any further. I am looking for an easier way to find the solution without having to...
  39. MironeDagains

    Solve Trig Equation with 2 & -Π/6 Inside Brackets

    http://www5a.wolframalpha.com/Calculate/MSP/MSP238521i5b83i951f19c3000010ca05be63f0bfc0?MSPStoreType=image/gif&s=10&w=219.&h=85. How do I solve this? I know the answers, as Wolphram Alpha has given me only the answers without any steps to how they derived those answers. I know that sin(x)=√3/2...
  40. Oribe Yasuna

    Integrating dx / (4+x^2)^2 using Trigonometric Substitution

    Homework Statement Evaluate the integral: integral of dx / (4+x^2)^2 Homework Equations x = a tan x theta a^2 + x^2 = a^2 sec^2 theta The Attempt at a Solution x = 2 tan theta dx = 2sec^2 theta tan theta = x/2 integral of dx / (4+x^2)^2 = 1/8 integral (sec^2 theta / sec^4 theta) d theta =...
  41. S

    Solving hyperbolic trigonometric equations

    Homework Statement Show that the real solution ##x## of $$tanhx=cosechx$$ can be written in the form ##x=ln(a \pm \sqrt{a})## and find an explicit value for ##a##. Homework Equations $$cosh^{2}x-sinh^{2}x=1$$ $$coshx=\frac{e^{x}+e^{-x}}{2}$$ The Attempt at a Solution I reduced the original...
  42. F

    Limit with trigonometric and polynomial function.

    Homework Statement For $$\lim _{ x\rightarrow \infty }{ \frac { { x }^{ 2 }+{ e }^{ -{ x }^{ 2 }\sin ^{ 2 }{ x } } }{ \sqrt { { x }^{ 4 }+1 } } } $$, determine whether it exists. If it does, find its value. if it doesn't, explain. Homework Equations Sand witch theorem and arithmetic rule...
  43. A

    Inverse trigonometric function integration

    I'm struggling to solve the following integral ∫ x/(√27-6x-x2) my attempt is as follows: ∫x/(√36 - (x+3)2) = ∫1/ √(36 - (x+3)2) + ∫x+1/ √(36 - (x+3)2) = arcsin (x + 3)/6 + this is where I got stuck.
  44. C

    Integration via Trigonometric Substitution

    Homework Statement Evaluate \int{\frac{x^2}{(1-x^2)^\frac{5}{2}}}dx via trigonometric substitution. You can do this via normal u-substitution but I'm unsure of how to evaluate via trigonometric substitution. Homework EquationsThe Attempt at a Solution Letting x=sinθ...
  45. anemone

    MHB Can You Solve This Trigonometric Equation for $x$?

    Solve for $x$ such that $2\sin(x+30^\circ)\sin 16^\circ \sin 76^\circ=\sin 2028^\circ \sin 210^\circ$ for $0\lt x \lt 180^\circ$.
  46. C

    MHB Trigonometric Identities Problem

    1) If \tan(\pi/4)=1, find \cot(\pi-\pi/4). 2) If \cot(17^{\circ}) = 3.2709, find \tan(73^{\circ}) 3) If \cot(\theta) = \frac{-9}{2} with \theta in Quadrant II, find \sin (\theta) --------------------------------------------- I really have no idea how to solve any of these problems. I have...
  47. O

    Derivative of a trigonometric function

    Homework Statement \frac{d}{dx}7.5sin(\frac{pi}{10}x) The Attempt at a Solution 7.5(\frac{pi}{10})cos(\frac{pi}{10}x) Maximum: f'(x) = 0 7.5(\frac{pi}{10})cos(\frac{pi}{10}x) = 0 7.5(\frac{pi}{10})cos^{-1}(0)= \frac{pi}{10}x ** (\frac{pi}{10}\frac{10}{pi})7.5(90) = x (1)(7.5)(90) = x...
  48. M

    Integration: inverse trigonometric functions

    Homework Statement ∫(t/√(1-t4))dt Homework Equations ∫(du/√(a2 - u2)) = arcsin (u/a) + C ∫(du/(a2 + u2) = (1/a) arctan (u/a) ∫(du/(u√(u2 - a2))) = (1/a) arcsec (|u|/a) The Attempt at a Solution Edit: I meant to write u where t2 is[/B]
  49. Rectifier

    Proving Trigonometric Identity: tan(x/2) = (1-cos(x))/sin(x)

    The problem Show that the left side is equal to right side ## tan (\frac{x}{2}) = \frac{1-cos(x)}{sin(x)} ## The attempt ##\tan(\frac{x}{2}) = \frac{ sin(\frac{x}{2}) }{ cos (\frac{x}{2}) } = \frac{ sin^2(\frac{x}{2}) }{ cos ^2 (\frac{x}{2}) } = \frac{\frac{1-cos(x)}{2}}{\frac{1+cos(x)}{2}} =...
  50. P

    Why do we assume certain values for theta and x in trigonometric substitutions?

    http://tutorial.math.lamar.edu/Classes/CalcII/TrigSubstitutions.aspx In example one, the author drops the absolute value bars and makes the following statement: "Without limits we won’t be able to determine if ##\tan{\theta}## is positive or negative, however, we will need to eliminate them in...
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