
easy trigo question
Id like to.confirm, cos(180a) is cosa right? I was reviewing my.past.notes and realised one question where I had stated that cos(180a)=cosa. It goes.like this " given that tana=3/4 and sinb=4/5, and that A and b are in the same quadrants, evaluate cos(180a).If you ask me.mow, my answer will.be 3/5 but my answer then was 3/5? Which of me is correct, thank for helping!

Re: easy trigo question
make use of the difference identity for cosine ...
$\displaystyle \cos(xy) = \cos{x}\cos{y} + \sin{x}\sin{y}$

Re: easy trigo question

Re: easy trigo question
Quote:
Originally Posted by
Tutu So cos(180a) is cosa?
did you use the given identity?