Question

If sin3 A = cos (A-26degree),Where 3A is an acute angel, find the value of A

Answer 1

Given us,
3a is an acute angle
sin3a = cos(a - 26)
=> cos(90-3a)= cos(a -26)
=> 90 - 3a = a - 26
=> -3a - a = - 26-90
=> -4a = -116
=> a = -116/-4
=> a = 29
hence, a= 29
______________________________

Answer 2

sin 3A=cos(A − 26)
⇒ cos(90 − 3A) = cos(A − 26)
⇒ (90 − 3A) = (A − 26)
⇒ 4A = 116°
∴ A = 29°