sinA + cosA = ½. cos4A=
Matematika
smangka17
Pertanyaan
sinA + cosA = ½. cos4A=
1 Jawaban
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1. Jawaban Anonyme
sin A + cos A = 1/2
(sin A + cos A)² = (1/2)²
sin² A + cos² A + 2 sin A cos A = 1/4
1 + sin 2A = 1/4
sin 2A = 1/4 - 1
sin 2A = -3/4
cos 4A
= cos 2(2A)
= 1 - 2 sin² 2A
= 1 - 2(-3/4)²
= 1 - 18/16
= (16 - 18)/16
= -2/16
= -1/8