SSC CHSL 20 Dec 2015 Shift 1 Paper

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Question : 150 of 200

Marks: +1, -0

If cos 20°= m and cos 70° = n, then the value of

m^2+n^2

is

$1/2$
1
$1/√2$
$3/2$

Solution:

m^2 + n ^2= cos ^2 20° + cos 70°

⇒

cos ^2 (90 °− 20 °) + cos 70°

⇒ sin ^2 70 °+ cos^2 70 °

⇒

1 ( ∵ sin ^2θ + cos ^2θ = 1)

Hence, option B is the correct answer.

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