mohon bantuannya,, di mohon, pake caranya..

Bab Trigonometri
Matematika SMA Kelas XI

aturan sinus
b/sin B = c/sin C
10/sin 30° = 15/sin C
sin C = 15 : ( 2 x 10)
sin C = 15/20 = y/r

Tripel Pitagoras
x = √(r² - y²)
x = √(20² - 15²)
x = √(400 - 225)
x = √175
x = 5√7

cos C = x/r = (5√7)/20 = 1/4 √7