No 6 dan 8. Mohon gunakan cara

Bab Trigonometri
Matematika SMA Kelas X

6] 1 - (sin² x)/(1 + cos x)
= (1 + cos x - sin² x)/(1 + cos x)
= (cos x + 1 - sin² x) / (1 + cos x)
= (cos x + cos² x) / (1 + cos x)
= cos x (1 + cos x) / (1 + cos x)
= cos x
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8] (1 - 2 cos² a) / (sin a cos a)
= (2 cos² a - 1) / (- sin a cos a)
= (cos² a - sin² a) / (- sin a cos a)
= (sin² a - cos² a) / (sin a cos a)
= (sin² a /(sin a cos a)) - (cos² a /(sin a cos a))
= tan a - cot a
terbukti