Jika sin (π/6-x) = cos x, tunjukan bahwa cos x= -√3

Terbukti nilai cosx=-√3

Jawab

sin (π/6 -x )= cos x
sin π/6  cos x – cos π/6 sin x = cos x
1/2 cos x – 1/2 √3 . sin x = cos x  } bagi   cos x
1/2 – 1/2 √3  tan x = 1
– 1/2 √3 tan x = 1 – 1/2 =  1/2
tan x = 1/2 / – 1/2√ 3
tan x= – 1/√3 = tan (-30) =  – tan 30 = tan 150
cos x = cos (150) = – cos 30 = – 1/2 √3
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