buktikan bahwa ( cosx + cos x )2 - ( sin x - cos x )2 = 4 sin x cos x
Matematika
meria100
Pertanyaan
buktikan bahwa ( cosx + cos x )2 - ( sin x - cos x )2 = 4 sin x cos x
1 Jawaban
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1. Jawaban bapakdr
(sin x + cos x)² - (sin x - cos x)²
= sin²x + cos²x + 2.sin x.cos x - (sin²x + cos²x - 2.sin x.cos x)
= 1 + 2.sin x.cos x - (1 - 2.sin x.cos x)
= 1 + 2.sin x.cos x - 1 + 2.sin x.cos x
= 4.sin x.cos x