Math  /  Trigonometry

Question4) cot2θ=cos2θ1cos2θ\cot ^{2} \theta=\frac{\cos ^{2} \theta}{1-\cos ^{2} \theta}

Studdy Solution

STEP 1

1. The equation involves trigonometric identities.
2. We will use the Pythagorean identity to simplify the expression.
3. We assume θ\theta is an angle where the trigonometric functions are defined.

STEP 2

1. Recognize and apply trigonometric identities.
2. Simplify the right-hand side of the equation.
3. Verify the equality.

STEP 3

Recognize that the right-hand side of the equation cos2θ1cos2θ\frac{\cos^2 \theta}{1 - \cos^2 \theta} can be simplified using the Pythagorean identity. The identity states:
sin2θ+cos2θ=1 \sin^2 \theta + \cos^2 \theta = 1
From this, we can express 1cos2θ1 - \cos^2 \theta as:
1cos2θ=sin2θ 1 - \cos^2 \theta = \sin^2 \theta

STEP 4

Substitute the expression for 1cos2θ1 - \cos^2 \theta into the right-hand side of the equation:
cos2θ1cos2θ=cos2θsin2θ \frac{\cos^2 \theta}{1 - \cos^2 \theta} = \frac{\cos^2 \theta}{\sin^2 \theta}
Recognize that this expression is equivalent to cot2θ\cot^2 \theta, since:
cotθ=cosθsinθ \cot \theta = \frac{\cos \theta}{\sin \theta}
Thus:
cot2θ=cos2θsin2θ \cot^2 \theta = \frac{\cos^2 \theta}{\sin^2 \theta}

STEP 5

Verify the equality by confirming that both sides of the original equation are indeed equal:
The left-hand side is cot2θ\cot^2 \theta, and the right-hand side simplifies to cos2θsin2θ\frac{\cos^2 \theta}{\sin^2 \theta}, which is also cot2θ\cot^2 \theta.
Therefore, the equation holds true:
cot2θ=cos2θ1cos2θ \cot^2 \theta = \frac{\cos^2 \theta}{1 - \cos^2 \theta}
The equality is verified and holds true for the given trigonometric identity.

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