Math Problem Statement

Let 0 be an angle such that sin0 =-(3/4) and cot0>0 find the exact values of tan0 and sec0

Solution

We are tasked with finding the exact values of tanθ\tan\theta and secθ\sec\theta given the conditions:

  1. sinθ=34\sin\theta = -\frac{3}{4}
  2. cotθ>0\cot\theta > 0.

Step 1: Analyze the quadrant

  • Since sinθ=34\sin\theta = -\frac{3}{4}, θ\theta must be in either the third or fourth quadrant, where sine is negative.
  • Given cotθ>0\cot\theta > 0, and since cotθ=cosθ/sinθ\cot\theta = \cos\theta / \sin\theta, this means that cosθ\cos\theta and sinθ\sin\theta have the same sign. This only happens in the third quadrant (where both sine and cosine are negative).
    Thus, θ\theta is in the third quadrant.

Step 2: Use the Pythagorean identity

The Pythagorean identity is:
sin2θ+cos2θ=1\sin^2\theta + \cos^2\theta = 1
Substituting sinθ=34\sin\theta = -\frac{3}{4}:
(34)2+cos2θ=1\left(-\frac{3}{4}\right)^2 + \cos^2\theta = 1
916+cos2θ=1\frac{9}{16} + \cos^2\theta = 1
cos2θ=1916=1616916=716\cos^2\theta = 1 - \frac{9}{16} = \frac{16}{16} - \frac{9}{16} = \frac{7}{16}
cosθ=716=74\cos\theta = -\sqrt{\frac{7}{16}} = -\frac{\sqrt{7}}{4}
(The cosine is negative because θ\theta is in the third quadrant.)

Step 3: Find tanθ\tan\theta

tanθ=sinθcosθ=3474=37=377\tan\theta = \frac{\sin\theta}{\cos\theta} = \frac{-\frac{3}{4}}{-\frac{\sqrt{7}}{4}} = \frac{3}{\sqrt{7}} = \frac{3\sqrt{7}}{7}

Step 4: Find secθ\sec\theta

The secant is the reciprocal of cosine:
secθ=1cosθ=174=47=477\sec\theta = \frac{1}{\cos\theta} = \frac{1}{-\frac{\sqrt{7}}{4}} = -\frac{4}{\sqrt{7}} = -\frac{4\sqrt{7}}{7}

Final Answers:

  • tanθ=377\tan\theta = \frac{3\sqrt{7}}{7}
  • secθ=477\sec\theta = -\frac{4\sqrt{7}}{7}

Would you like a step-by-step explanation of the trigonometric reasoning or more examples?

Here are some related questions:

  1. What are the values of cotθ\cot\theta and cscθ\csc\theta for this angle?
  2. How do signs of trigonometric functions change in each quadrant?
  3. What is the significance of the Pythagorean identity in trigonometry?
  4. How can you determine an angle’s quadrant based on trigonometric values?
  5. What is the relationship between reciprocal trigonometric functions?

Tip: Always check the quadrant carefully before determining the signs of trigonometric functions!

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Pythagorean Identity
Trigonometric Functions
Quadrants of Trigonometric Functions

Formulas

sin^2θ + cos^2θ = 1
tanθ = sinθ / cosθ
secθ = 1 / cosθ
cotθ = cosθ / sinθ

Theorems

Pythagorean Identity
Signs of Trigonometric Functions in Different Quadrants

Suitable Grade Level

Grades 9-12