Question

Tolong bantu...

pakai cara ya...

Answer 1

Sin 40 = a
sin 50 = b
Maka,
cos 130 = cos(180-50)
Aturan kuadran II
cos 130 = -cos 50
Identitas:
cos 130 = -sin(90-50)
cos 130 = -sin 40
cos 130 = -a

Answer 2

Cos 130°= sin (90+40)
= sin 40°

sin 40°= a