If sec 4A = cosec(A – 20), where 4A is an acute angle, find the value of A.

Solution :

Given,  sec 4A = cosec(A – 20)

\(\implies\)  cosec(90 – 4A) = cosec(A – 20)

\(\implies\)  90 – 4A = A – 20

\(\implies\)  5A = 110

\(\implies\)  A = 22