Untuk 30a bagaimana pembuktiannya?

(cot α + csc α)² = (1 + cos α)/(1 - cos α)
( cos α/sin α + 1/sin α )² = (1 + cos α)/(1 - cos α)
[ (cos α + 1) / sin α ]² = (1 + cos α)/(1 - cos α)
[ (cos α + 1)² / sin² α ] = (1 + cos α)/(1 - cos α)

karena
sin² α = 1 - cos²α
maka

[ (cos α + 1)² / (1 - cos²α) = (1 + cos α)/(1 - cos α)

ingat:
1 - cos²α = (1 - cos α)(1 + cos α)
maka

[ (cos α + 1)² / ( (1-cos α)(1+cos α) ) = (1 + cos α)/(1 - cos α)

(cos α + 1) / (1 - cos α) = (1 + cos α)/(1 - cos α)
(1 + cos α)/(1 - cos α) = (1 + cos α)/(1 - cos α)

terbukti

semoga membantu