Question

What is the value of x?
sin(x+21)°=cos(2x+21)°

Answer 1

we know that
if sin A=cos B
then
angle A and angle B are complementary angles
so
A+B=90°

in this problem
(x+21)+(2x+21)=90-------> 3x+42=90-------> 3x=48-----> x=16°