If sin θ + cos θ = 1, then the value of sin 2θ is equal to

(A) 1 

(B)1/2 

(C) 0 

(D) –1

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1 Answers

Answer is (C)

Given,

 sin θ + cos θ = 1

Sq. both side

(sin θ + cos θ)2 = 12

sin2 θ + cos2 θ + 2sin θ .cos θ = 1

1 + 2sin θ .cos θ = 1

2sin θ .cos θ = 1 -1 = 0

sin 2θ = 0   (sin 2θ = 2sin θ .cos θ )

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