soo okay...i have this question that im stuck on...(adsbygoogle = window.adsbygoogle || []).push({});

Solve for x,

cos 2x - cos^2x = 0, -180degrees<x<180degrees

i tried solving it...

cos 2x - cos^2x = 0

[2cos^2x -1]-cos^2x = 0

cos^2x -1 = 0 <--(???)

(cos x -1)(cos x +1) = 0

therefore... 1)cos x = -1 , 2)cos x = 1

so...

1)cos x = -1

x = cos^-1 (-1)

x= 180

2) cos x = 1

x = 0

but i have tried on my calculator...and -180 degrees can be one of the answers too...i dont get how to get -180

SOMEONE HELPP...and reply FASTT plz and Thank yOU in advance

**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: HELP Trig Equation

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