PEMBAHASAN
Trigonometri
koreksi soal
sin A sin B = 1/4
A + B = π/3 = 180°/3 = 60°
cos (A + B) = cos 60°
cos A cos B - sin A sin B = 1/2
cos A cos B - 1/4 = 2/4
cos A cos B = 2/4 + 1/4
cos A cos B = 3/4
cos (A - B)
= cos A cos B + sin A sin B
= 3/4 + 1/4
= 4/4
= 1
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Verified answer
PEMBAHASAN
Trigonometri
koreksi soal
sin A sin B = 1/4
A + B = π/3 = 180°/3 = 60°
cos (A + B) = cos 60°
cos A cos B - sin A sin B = 1/2
cos A cos B - 1/4 = 2/4
cos A cos B = 2/4 + 1/4
cos A cos B = 3/4
cos (A - B)
= cos A cos B + sin A sin B
= 3/4 + 1/4
= 4/4
= 1