Question

find the value of cos10.cos30.cos50.cos70.​

Answer 1

Answer:

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Step-by-step explanation:

cos 10°.cos 30°.cos 50°.cos 70°.​

cos 30°(cos 10°.cos 50°.cos 70°)

1/2(cos 10°.cos 50°.cos 70°) (equation 1)

(cos 10°.cos 50°.cos 70°)

by using

cos a°.cos (60+a)°.cos(60-a)°=cos 3a°/4

(cos 10°.cos (60-10)°.cos (60+10)°)=(cos 3×10°)/4

cos 30°=1/2

1/2/4=1/8

sub in equation 1

1/2*1/8

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