Question

If sin (x-20)°=cos(3x-10)° then find the value of x

Answer 1

$sin x = cos (90-x)$

By that property:

$sin (x-20) = cos(90-x+20)$

Hence:

$cos(90-x+20)=cos(3x-90)\\ 90-x+20=3x-90\\ x=50$