I am currently learning how to simplify trig functions, but is there a way to know which formulae to use?(adsbygoogle = window.adsbygoogle || []).push({});

In my text book there are three formulae:

cos^2ttheta + sin^2theta = 1

1 + tan^2theta = sec^2theta

cot^2theta + 1 = cosec^2theta

I am also stuck in this question:

prove this identity:

cosA / (1 - tanA) + sinA / (1 - cotA) = Sin A + cosA

Since this requires a proof I need to work on the LHS and RHS separately. Can someone help me start this question? I really appreciate your help.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Simplifying trig functions

**Physics Forums | Science Articles, Homework Help, Discussion**