NEW Beginner's Trigonometry Identities Problem

In summary, the conversation discusses finding the sine function when cosine is given in Quadrant II and asks if there is an identity relating sine and cosine. The use of Latex is also mentioned.
  • #1
courtbits
15
0
Alright. I am sort of understanding this section on my online math lesson, but I am still struggling with it. Would be gladly appreciated if someone could help me with this:

If cosΘ = -4/9 with Θ in Quadrant II, find sinΘ
 
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  • #2
I want to ask you 2 questions:

  • What is the sign of the sine function in Quadrant II?
  • Is there an identity that can relate sine and cosine, that is, sine and cosine are the only two trig. functions present in the identity?
 
  • #3
MarkFL said:
I want to ask you 2 questions:

  • What is the sign of the sine function in Quadrant II?
  • Is there an identity that can relate sine and cosine, that is, sine and cosine are the only two trig. functions present in the identity?

1) I have no idea what you are asking. v~v <== Dunce
2) Umm.. \(\displaystyle {sin}^{2}\theta + {cos}^{2}\theta = 1\) ...I think. o-o"

YAAS. I figured out how to use the Latex stuff. :D
 
Last edited:
  • #4
courtbits said:
1) I have no idea what you are asking. v~v <== Dunce
2) Umm.. \(\displaystyle {sin}^{2}\theta + {cos}^{2}\theta = 1\) ...I think. o-o"

YAAS. I figured out how to use the Latex stuff. :D

1.) Picture the unit circle, and a point on the circle in Quadrant II...is the $y$-coordinate positive or negative?

2.) Yes, good...since you are being asked to find the sine function, can you solve this identity for $\sin(\theta)$? And then the answer to part 1.) will tell you which root to take.

3.) Good job using $\LaTeX$. One suggestion...precede the trig. functions with a backslash, and they will not be italicized which makes them look like string of variables rather than pre-defined functions. For example, the code:

\sin^2(\theta)+\cos^2(\theta)=1

produces:

$\sin^2(\theta)+\cos^2(\theta)=1$

Also, for clarity, it is always a good idea to enclose the arguments of the functions in bracketing symbols...this way everyone knows exactly what the angle is. :D
 

FAQ: NEW Beginner's Trigonometry Identities Problem

What is Trigonometry?

Trigonometry is a branch of mathematics that deals with the relationships between the sides and angles of triangles. It is used to calculate unknown angles and sides of a triangle, and to solve problems involving angles and distances.

What are Trigonometric Identities?

Trigonometric identities are equations that involve trigonometric functions and are always true for all values of the variables in the equation. They are used to simplify and manipulate trigonometric expressions and equations.

What is the importance of knowing Trigonometric Identities?

Knowing trigonometric identities is important in solving more complex trigonometric problems and equations. They also help in understanding the relationships between different trigonometric functions and how they can be used to solve real-world problems.

How do I use Trigonometric Identities?

To use trigonometric identities, you must first understand the basic trigonometric functions (sine, cosine, and tangent) and their properties. Then, you can apply the identities to simplify expressions or solve equations by substituting known values and manipulating the equations.

Are there any tips for learning Trigonometric Identities?

Practice is key when learning trigonometric identities. Make sure to familiarize yourself with the basic identities and their properties, and then move on to more complex ones. It also helps to understand the geometric meanings behind the identities and how they relate to the unit circle.

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