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Himpunan Penyelesaian Dari Cos^2 x – 4 Cos x – 5 = 0

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 JAWABAN: B

PEMBAHASAN:

cos2 x – 4 cos x – 5 = 0

misal cos x = A

cos2 x – 4 cos x – 5 = 0

A2 – 4A – 5 = 0

(A - 5)(A + 1) = 0

A = 5 | A = -1

cos x = 5 | cos x = -1

cos x = 5 tidak bisa dikerjakan

cos x = -1

cos x = cos π

Pertama

x = π + k.2π

x = π

Kedua

x = - π + k.2 π

x = π

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