Question

Diketahui a + b = 90 derajat dan cos a = 2/3 tan b. nilai secan^2 b

Answer 1

A = 90 - b
cos a = cos (90 - b) = sin b = 2/3 tan b
sin b = 2/3  .sin b /cos b  [ coret sin b kanan dan kiri ]
1 = 2/3 . 1/cos b 

3/2 = 1/ cos b { kuadratkan kanan dan kiri }
9/4 = 1/ cos² b       [ sec b = 1/cos b]
9/4 = sec² b