What is Trigonometry: Definition and 660 Discussions

Trigonometry (from Greek trigōnon, "triangle" and metron, "measure") is a branch of mathematics that studies relationships between side lengths and angles of triangles. The field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies. The Greeks focused on the calculation of chords, while mathematicians in India created the earliest-known tables of values for trigonometric ratios (also called trigonometric functions) such as sine.Throughout history, trigonometry has been applied in areas such as geodesy, surveying, celestial mechanics, and navigation.Trigonometry is known for its many identities. These
trigonometric identities are commonly used for rewriting trigonometrical expressions with the aim to simplify an expression, to find a more useful form of an expression, or to solve an equation.

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  1. X

    Trigonometry Obscurity: Solving Triangle ABC

    Hey everyone, I was looking over some old pre-calculus exams and I found this rather obscure looking question.. It's about trigonometry. You're given a triangle ABC, and the legs are a (BC),b (AC), c (AB). You're given the lenghts of a=5, b-8, and the angle C between them is 140. The...
  2. C

    Solving cos^-1 (3/7): Exact Trigonometric Values and Techniques

    Hello all In my textbook I encountered the following problem: Find the six trigonometric values of cos^ -1 (3/7). They must be exact. I gather what they mean is that I find arccos (3/7). I tried applying basic identities, but didn't work. Any help would be appreciated. Thanks
  3. K

    Trigonometry identity proof trouble. (Help much appreciated)

    I can do pretty much all the proofs except these two, though I've tried to make a start. Note that in the questions the angle is given as theta, but for the sake of my keyboard I've changed it to angle 'x'. Q15: Prove: Tan2xsecx = 2sinxsec2x. So I need to show the two sides are equal...
  4. denian

    Trigonometry homework help question

    in triangle PQR, PQ = a, QR = a + d, RP = a + 2d, and angle PQR is more than 120 degree., where a and d are positive constants. show that 2a/3 < d < a. i tried to think, but i really don't know how to start to solve this question. hope for some clue. thank you
  5. M

    I've created some new formulas in trigonometry (perhaps)

    Hi all, I'm a newbie here and sorry for my bad English. I want to share with you guys 2 formulas I've created luckily on a boring day: 1) Let R be circumscribed circle of triangle ABC, let S be it's area. We have: S=2R^2*sinAsinBsinC 2)Let S be area of triangle ABC, a=BC, b=CA, c=AB. We...
  6. Alethia

    Solving a Trigonometry Proof: 1+ cos Ө =?

    Yes it is me again. :D Now with a trig problem XD I was doing some problems on my homework in math, Trigonometry and I had problems proving this proof: 1+ cos Ө = csc Ө + cot Ө I've worked it out until I simplified the right side to: sin Ө ----- 1+ cos Ө And then I realized...
  7. J

    Can You Solve This Trigonometry Problem Involving Equal Sides and Angles?

    In the figure, EA=EB=EC and AB = 200 m. Angle BCA = 30 degrees. Find angle AEB. Anyone can help me?
  8. M

    Help with some trigonometry problems please

    help with some trigonometry problems please! hello everybody! how's everyone doing? i hope you guys are well and your homework is going great! i posted another help thread but it was in the wrong section! sorry! but i got great help there! :smile: :smile: ok here's my new problem. i tried...
  9. Juntao

    Sail Boat Race Trigonometry, just stuck on first part

    I've added a picture that's part of the problem. A sailboat race course consists of four legs defined by the displacement vectors A, B, C and D shown above. The values of the angles are È1 = 420, È2 = 410, and È3 = 270. The magnitudes of the first three vectors are A = 3.7 km, B = 5.3 km...
  10. zeronem

    I have enrolled in a Trigonometry Class in College.

    Anyways as I said, I put myself in a Trigonometry class. I got into this Continued Learning Program at a Small College in which they will let me take Trigonometry and I will not get any Credits from it, therefore they will not put this class in my School Records. I am basically taking it on my...
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