Math  /  Trigonometry

QuestionQuestion 5 (1 point) 1cot2θ+secθcosθ\frac{1}{\cot^2\theta} + \sec\theta \cos\theta
csc2θ tan2θ sec2θ 1

Studdy Solution

STEP 1

What is this asking? We need to simplify a trigonometric expression involving cotangent, secant, and cosine. Watch out! Remember the fundamental trigonometric identities and be careful not to mix them up!

STEP 2

1. Rewrite in terms of sine and cosine
2. Simplify the expression
3. Apply the Pythagorean identity

STEP 3

Let's **rewrite** everything in terms of sine and cosine!
This usually makes things much clearer.
We know that cotθ=cosθsinθ\cot\theta = \frac{\cos\theta}{\sin\theta}, so cot2θ=cos2θsin2θ\cot^2\theta = \frac{\cos^2\theta}{\sin^2\theta}.
Therefore, 1cot2θ=1cos2θsin2θ=sin2θcos2θ\frac{1}{\cot^2\theta} = \frac{1}{\frac{\cos^2\theta}{\sin^2\theta}} = \frac{\sin^2\theta}{\cos^2\theta}.

STEP 4

Also, we know secθ=1cosθ\sec\theta = \frac{1}{\cos\theta}.
So, secθcosθ=1cosθcosθ=1\sec\theta \cdot \cos\theta = \frac{1}{\cos\theta} \cdot \cos\theta = 1.
We're multiplying by cosθcosθ=1\frac{\cos\theta}{\cos\theta}=1 to add to one.

STEP 5

Now, let's put it all together!
Our original expression becomes: 1cot2θ+secθcosθ=sin2θcos2θ+1 \frac{1}{\cot^2\theta} + \sec\theta \cdot \cos\theta = \frac{\sin^2\theta}{\cos^2\theta} + 1

STEP 6

Since tanθ=sinθcosθ\tan\theta = \frac{\sin\theta}{\cos\theta}, we have tan2θ=sin2θcos2θ\tan^2\theta = \frac{\sin^2\theta}{\cos^2\theta}.
So, our expression is now tan2θ+1\tan^2\theta + 1.
Getting close!

STEP 7

One of the **most important** trigonometric identities is sin2θ+cos2θ=1\sin^2\theta + \cos^2\theta = 1.
If we divide both sides of this identity by cos2θ\cos^2\theta, we get: [ \frac{\sin^2\theta}{\cos^2\theta} + \frac{\cos

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