Question

need help with these questions

http://locker.palcs.org/~jbaskwill/pc/5-4practice.pdf

Answer 1

cos x=sin 2x,
cos x -sin 2x =0,
cos x -(2sin x cos x=0,
cos x(1-2sin x)=0, equate to zero...
cos x=0 and 1-2sin x=0,
1= 2 sin x
1/2 = sin x
x =arc cos 0 and x= arc sin 1/2
x=pi/2 and x=pi/6

Answer 2

check cos(pi/2)=sin(2xpi/2)
0 = o true
cos(3pi/2)=sin2(3pi/2)
0=0 true
A ans pi/2, 3pi/2