cos 40° +cos 80°+ cos 160° =
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cos 40° +cos 80°+ cos 160° =
1 Jawaban
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1. Jawaban Ryanenrico15
cos 80 + cos 40 + cos 160
=(2.cos (80+40)/2. cos (80-40)/2 ) + cos 160
= 2cos 60. cos 20 + cos 160
=2.1/2 .cos 20 + cos 160
= cos 160+ cos 20
= 2. cos (160+20)/2 .cos (160-20)/2
= 2 .cos 90. cos 70
=2. 0.cos 70
=0