Question

If sin (3x+2) = cos (6x+7), then what is the value of x?
a) 1
b) 4
c) 9
d) 19

Answer 1

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

therefore
(3x+2)+(6x+7)=90--------> 9x+9=90------> 9x=90-9----> x=81/9----> x=9°

the answer is
x=9