Math

QuestionProve that sin3θ+sinθ=4sinθ4sin3θ\sin 3\theta + \sin \theta = 4 \sin \theta - 4 \sin^3 \theta.

Studdy Solution

STEP 1

Assumptions1. We are dealing with trigonometric identities. . The variable θ\theta represents an angle in radians or degrees.
3. The symbol \equiv means "is identically equal to", which means the equation holds true for all values of θ\theta.

STEP 2

We know the trigonometric identity for sinθ\sin\theta is given bysinθ=sinθ4sinθ\sin\theta =\sin\theta -4\sin^\theta

STEP 3

Substitute the identity of sin3θ\sin3\theta into the given equation.
sin3θ+sinθsinθsin3θ\sin3\theta + \sin\theta \equiv\sin\theta -\sin^3\thetabecomes3sinθsin3θ+sinθsinθsin3θ3\sin\theta -\sin^3\theta + \sin\theta \equiv\sin\theta -\sin^3\theta

STEP 4

implify the left-hand side of the equation by combining like terms.
4sinθ4sin3θ4sinθ4sin3θ4\sin\theta -4\sin^3\theta \equiv4\sin\theta -4\sin^3\theta

STEP 5

Now, we can see that the left-hand side of the equation is identical to the right-hand side of the equation, which verifies the given identity.
Therefore, we have shown thatsin3θ+sinθ4sinθ4sin3θ\sin3\theta + \sin\theta \equiv4\sin\theta -4\sin^3\theta

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