Friday

October 24, 2014

October 24, 2014

Posted by **emily** on Tuesday, April 26, 2011 at 9:47pm.

cos2x=cosx

- identities trig? -
**MathMate**, Tuesday, April 26, 2011 at 9:51pm - identities trig? -
**Reiny**, Tuesday, April 26, 2011 at 9:51pmcos 2x = cosx

2cos^2 x - 1 - cosx = 0

(2cosx + 1)(cosx -1) = 0

cosx = -1/2 or cosx = 1

if cosx = -1/2, x is in II or III

x = 2π/3 or 4π/3 ......I knew cos π/3 = +1/2

if cosx = 1, then x = 0 or x = 2π

**Answer this Question**

**Related Questions**

Precalculus - Please help!!!!!!!!!!! Find all solutions to the equation in the ...

calculus - Find all solutions to the equation in the interval [0,2pi) Cosx-cos2x

trig - Find ALL solutions to the equation on the interval [0, 2pie]: 2sin(1/2X...

trip - for sin2x+cosx=0, use double-angle or half-angle formula to simplify the ...

pre calc - cos2x=cosx in interval of [0,2pie]

trig - Find all solutions of the equation 2sin^2x-cosx=1 in the interval [0,2pi...

Pre-Calculus - Find all solutions to the equation in the interval [0, 2pi) cos4x...

Pre calc - Find solutions on interval 0,2pie (cosx/1+sinx) + (1+sinx/cosx) = -4

Trig. - Can someone please help me with this? Find all solutions to the equation...

Math, please help - Which of the following are trigonometric identities? (Can be...