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If sin⁡θ+cos⁡θ=√2, then what is the value of 8sin⁡θcos⁡θ ?
Question

If sin⁡θ+cos⁡θ=√2, then what is the value of 8sin⁡θcos⁡θ ?

A.

2

B.

16

C.

8

D.

4

Correct option is D

 Given:

sin⁡θ+cos⁡θ= 2\sqrt 2​​

Formula Used:
sin2x+cos2xsin^2 x + cos^2 x​ = 1
Solution:
sin⁡θ+cos⁡θ=√2
By, squaring both sides of the above equation we get,
=>[sinθ+cosθ]2=[2]2[sin⁡θ+cos⁡θ]^2=[{\sqrt2}]^2
=> sin2θ+cos2θ+2sinθ.cosθ=2sin^2 θ + cos^2 θ + 2sin θ.cos θ = 2​​
As we know that, sin2x+cos2xsin^2 x + cos^2 x ​= 1
=> 1 + 2sin θcos θ = 2
=> 2sin θcos θ = 2-1 = 1

Multiply by 4 both sides,

∴ 8sin θcos θ = 1×4=4\times 4 = 4​ 

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