Question

cos θ + cos 2θ = 1,the value of sin 2θ + sin 4θ is

Answer 1

Answer:

Correct option is

C

1

∵sinθ+sin

2

θ=1

⇒sinθ=1−sin

2

θ=cos

2

θ

Squaring both sides

sin

2

θ=cos

4

θ

cos

2

θ=cos

4

θ

cos

2

θ+cos

4

θ=cos

2

θ+sin

2

θ=1

Step-by-step explanation:

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Answer 2

Answer:

2cos(θ)sin(3θ)

Step-by-step explanation:

Use the Product Identity: sin(s)+sin(t)= 2sin($\frac{s+t\\}{2}$)cos($\frac{s-t}{2\\}$)=

2sin((2θ+4θ)/2)cos((2θ-4θ)/2)

Simpify:

2cos(θ)sin(3θ)