Tolong bantuin yakkk sin α cos(90o α) + cos α sin ( 90o - α) =1 -

Sin a cos(90 - a) + cos a sin(90 - a)
sin(a + (90 - a))
sin 90 = 1
atau
sin a cos(90 - a) + cos a sin(90 - a)
sin a. sin a + cos a. cos a
sin² a + cos² a = 1

Source https://sebuahcatatan.live/as/catatanbrain/tugas/2118576