mathtrigonometry
posted by Michael on .
I'm working woith multiple ange and product sum formulas and I'm stuck on these. Can you help? Thanks
sin2xsinx=cosx
cos2xcosx=0

are we solving?
1st one:
sin2xsinx=cosx
2sinxcosxsinx  cosx = 0
cosx(2sin^2 x  1) = 0
cosx = 0 or sin^2x = 1/2
if cosx=0,
x = π/2 or x=3π/2 (90° or 270°)
if sin^2x = 1/2
sinx = ±1/2
x = π/4 , 3π/4, 5π/4, or 7π/4 (45°, 135°, 225° or 315°)
for the 2nd
use cos 2x = 2cos^2x  1 to end up with a quadratic.
give it a try.
it will factor