4 cos 66degrees + sin 84degrees ) = root of 3 +root of 15
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Answered by
3
Answer:
√3 + √15
Step-by-step explanation:
1.cosC + cosD
= 2 cos((C+D)/2) cos((C-D)/2)
2. cos(36°) = √5 +1)/4
4(cos 66° + sin 84°)
=4(cos 66° + cos 6°)
= 4 × 2 cos((66°+6°)/2) cos((66°-6°)/2)
= 8 cos(36°) cos(30°)
= 8 × (√5 +1)/4 × (√3/2)
= (√5 +1) × (√3)
= √3 + √15.
Answered by
1
Answer:
√3 + √15
Step-by-step explanation:
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