Sin^2x-sin2x=3cos^2x

Question

Sin^2x-sin2x=3cos^2x

Answer 1

sin^2x-sin2x=3cos^2x

 sin^2x-2sinxcosx=3cos^2x  /cos^2x

tg^2x-2tgx-3=0

a^2-2a-3=0

D=4+12=16=4^2

x1=3;    x2=-1;

tgx=3

x=arctg 3+ Пn

tgx=-1

x= -П/4+Пn