a. 72/125
b.96/125
c. 108/125
d. 124/125
e. 144/125
Diketahui cos x = 3/5 untuk 0 < x< 90 nilai dari sin 3x + sin x adalah …..
sin 3x+sinx = 2sin(3x+x/2)×cos(3x-x/2)
= 2sin(4x/2)×cos(2x/2)
= 2sin2x×cosx
= 2(2sinxcosx)×cosx
= 4(√1-cos²x)cosx×cosx
= 4(√1-(3/5)²)(3/5)(3/5)
= 4(√25/25-9/25)(9/25)
= 4(√16/25)(9/25)
= 4(4/5)(9/25)
= 4(36)125
= 144/125