PREPARING Become a MATIZEN What is Math Planet ? A Crash Course on      Algebra A Crash Course on      Geometry   EXPLORING Advanced Math Topic Customized Lessons SAT & ACT Reviews   INTERACTING Math Games Discussion Forum Math Live! Chat   COLLECTING Math Search MATIZEN Qualifi-      -cation Test Acknowledgements The Creatures Behind      the Math Planet        ©1998 ThinkQuest        team 16284    All rights reserved

Trigonometry

y = -2 – 3sec(4x - P /2)

# The Identities of Trigonometry

Another important part of trigonometry is the trigonometric identity. Trigonometric identities are used to prove equations are the same and are used to solve the equations. There is nothing tricky about trigonometry identity. Once you memorize the formulas below, you will do well on it.

 Basics: sin^2x + cos^2x = 1      tanx = sinx / cosx      cotx = cosx /sinx      secx = 1 / cosx      cscx = 1 / sinx      cotx = 1 / tanx      1 + cot^2x = csc^2x      tan^2x + 1 = sec^2x
 Advanced: cos(a + b) = cos a cos b – sin a sin b      cos(a - b) = cos a cos b + sin a sin b      sin(a + b) = sin a cos b + cos a sin b      sin(a - b) = sin a cos b - cos a sin b      tan (a + b) = tan a + tan b / 1 – tan a tan b      tan (a - b) = tan a + tan b / 1 + tan a tan b      cos 2x = cos^2x – sin^2x      cos 2x = 1 – 2 sin^2x      cos 2x = 2 cos^2x – 1      sin 2x = 2 sinx cosx      tan 2x = 2tanx / 1 – tan^2x      cos x/2 = +-Ö (1 + cosy / 2)      sin x/2 = +- Ö (1 – cosy /2)      tan x/2 = sin y / 1 + cos y      tan x/2 = 1 – cosy / sin y      sin 3x = 3 sin x – 4 sin^3 x      cos 3x = 4 cos^3 x – 3 cos x     sin a + sin b = 2 sin ( a + b / 2) cos ( a - b / 2)      sin a - sin b = 2 cos ( a + b / 2) sin ( a - b / 2)      cos a + cos b = 2 cos ( a + b / 2) cos ( a - b / 2)      cos a – cos b = -2 sin ( a + b / 2) sin ( a - b / 2)

You can also jump to the chapter of your choice by using the drop-down list at below.