Master Math butuh cara penyelesaiannya soal ini!

CD = AC - AD

AC/sin B = p/sin(90 - B)
AC = p sin B/cos B

AD/sin a = p/sin (90 - a)
AD = p sin a/cos a

CD = p sin B/cos B - p sin a/cos a
CD = p (sin B cos a - cos B sin a)/(cos B cos a)
CD = p [sin (B - a)]/cos a cos B

ps: misalkan sudut beta = B, sudut alfa = a

Jawaban : A