Math Problem Statement

Find the exact value of each trigonometric function at the given real number: (a) \( \tan\left(-\frac{3\pi}{4}\right) \) (b) \( \csc\left(-\frac{3\pi}{4}\right) \) (c) \( \cot\left(-\frac{3\pi}{4}\right) \)

Solution

Let's solve each of these trigonometric function values for 3π4-\frac{3\pi}{4}.

(a) tan(3π4)\tan\left(-\frac{3\pi}{4}\right)

The tangent function is odd, meaning tan(x)=tan(x)\tan(-x) = -\tan(x). Therefore: tan(3π4)=tan(3π4)\tan\left(-\frac{3\pi}{4}\right) = -\tan\left(\frac{3\pi}{4}\right) Now, 3π4\frac{3\pi}{4} is in the second quadrant, where the tangent function is negative. The reference angle is π4\frac{\pi}{4}, so: tan(3π4)=1\tan\left(\frac{3\pi}{4}\right) = -1 Thus: tan(3π4)=(1)=1\tan\left(-\frac{3\pi}{4}\right) = -(-1) = 1

(b) csc(3π4)\csc\left(-\frac{3\pi}{4}\right)

The cosecant function is odd as well, meaning csc(x)=csc(x)\csc(-x) = -\csc(x). Therefore: csc(3π4)=csc(3π4)\csc\left(-\frac{3\pi}{4}\right) = -\csc\left(\frac{3\pi}{4}\right) In the second quadrant, where 3π4\frac{3\pi}{4} lies, the cosecant function is positive. Using the reference angle π4\frac{\pi}{4}, we know: csc(3π4)=csc(π4)=2\csc\left(\frac{3\pi}{4}\right) = \csc\left(\frac{\pi}{4}\right) = \sqrt{2} Thus: csc(3π4)=2\csc\left(-\frac{3\pi}{4}\right) = -\sqrt{2}

(c) cot(3π4)\cot\left(-\frac{3\pi}{4}\right)

The cotangent function is odd, so cot(x)=cot(x)\cot(-x) = -\cot(x). Thus: cot(3π4)=cot(3π4)\cot\left(-\frac{3\pi}{4}\right) = -\cot\left(\frac{3\pi}{4}\right) Since cot(3π4)=1\cot\left(\frac{3\pi}{4}\right) = -1 (as it’s the reciprocal of tan(3π4)\tan\left(\frac{3\pi}{4}\right)), we get: cot(3π4)=(1)=1\cot\left(-\frac{3\pi}{4}\right) = -(-1) = 1

Summary of Answers:

  1. tan(3π4)=1\tan\left(-\frac{3\pi}{4}\right) = 1
  2. csc(3π4)=2\csc\left(-\frac{3\pi}{4}\right) = -\sqrt{2}
  3. cot(3π4)=1\cot\left(-\frac{3\pi}{4}\right) = 1

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Related Questions:

  1. How would these values change if the angle were positive?
  2. What is the significance of odd and even functions in trigonometry?
  3. How do we determine reference angles for non-standard angles?
  4. What are the values of other trigonometric functions at 3π4-\frac{3\pi}{4}?
  5. How would we solve this problem in terms of degrees?

Tip:

For angles in the unit circle, knowing the quadrant helps determine the sign of each trigonometric function.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Unit Circle
Reference Angles

Formulas

\( \tan(-x) = -\tan(x) \)
\( \csc(-x) = -\csc(x) \)
\( \cot(-x) = -\cot(x) \)

Theorems

Odd Function Property of Trigonometric Functions

Suitable Grade Level

Grades 10-12