cos 195 drajat dikurangi cos 75 drajat

TriGonoMetRi

cos a - cos b = -2 sin (a+b)/2 sin (a-b)/2

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cos 195° - cos 75°
= -2 sin 135° sin 60°
= -2 sin 45° sin 60°
= -2 . 1/2 √2 . 1/2 √3
= -1/2 √6 ✔