Question

The value of cos 40° + cos20°
cos 40° + cos 20°​

Answer 1

Answer: Hope this helps

Answer 2

cos 40 + cos20° = √3cos10

Given:

cos 40 + cos20°

To Find:

The value of cos 40° + cos20°

Solution:

We know, cos a + cos b = $2cos(a+b)cos(a-b)/2$

$cos 40+ cos 20 = 2cos(40+20)cos(40-20)/2$

$cos40+cos20 = 2cos30cos20$

cos 40 + cos20° = 2*√3/2*cos10

⇒cos 40 + cos20° = √3cos10

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