Math Problem Statement

csc=-5/4 and tan>0 and find cot and sec

Solution

Given that:

  • cscθ=54\csc \theta = -\frac{5}{4}
  • tanθ>0\tan \theta > 0

We can find the values of cotθ\cot \theta and secθ\sec \theta.

Step 1: Understand the properties of trigonometric functions

  • cscθ=1sinθ\csc \theta = \frac{1}{\sin \theta}

    This gives: sinθ=1cscθ=154=45\sin \theta = \frac{1}{\csc \theta} = \frac{1}{-\frac{5}{4}} = -\frac{4}{5}

  • Since tanθ>0\tan \theta > 0, we know that both sinθ\sin \theta and cosθ\cos \theta must have the same sign (either both positive or both negative). Given that sinθ\sin \theta is negative, cosθ\cos \theta must also be negative.

Step 2: Use the Pythagorean identity

The identity for sine and cosine is: sin2θ+cos2θ=1\sin^2 \theta + \cos^2 \theta = 1

Substitute sinθ=45\sin \theta = -\frac{4}{5}: (45)2+cos2θ=1\left( -\frac{4}{5} \right)^2 + \cos^2 \theta = 1 1625+cos2θ=1\frac{16}{25} + \cos^2 \theta = 1 cos2θ=11625=25251625=925\cos^2 \theta = 1 - \frac{16}{25} = \frac{25}{25} - \frac{16}{25} = \frac{9}{25} \cos \theta = -\frac{3}{5} \quad \text{(since \cos \theta is negative in this case)}

Step 3: Find cotθ\cot \theta and secθ\sec \theta

  • cotθ=cosθsinθ\cot \theta = \frac{\cos \theta}{\sin \theta} cotθ=3545=34\cot \theta = \frac{-\frac{3}{5}}{-\frac{4}{5}} = \frac{3}{4}

  • secθ=1cosθ\sec \theta = \frac{1}{\cos \theta} secθ=135=53\sec \theta = \frac{1}{-\frac{3}{5}} = -\frac{5}{3}

Final Answer:

  • cotθ=34\cot \theta = \frac{3}{4}
  • secθ=53\sec \theta = -\frac{5}{3}

Would you like more details or clarification? Here are some related questions:

  1. How can you verify the values of trigonometric functions using the unit circle?
  2. What are the other trigonometric identities involving cot\cot and sec\sec?
  3. How do you determine the quadrant of an angle given the signs of the trigonometric functions?
  4. Can you derive the values of trigonometric functions using the values of sinθ\sin \theta and cosθ\cos \theta?
  5. What happens to these functions if tanθ<0\tan \theta < 0?

Tip: Always check the quadrant where the angle lies by looking at the signs of the trigonometric functions.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Cosecant
Tangent
Cotangent
Secant
Pythagorean Identity

Formulas

csc(θ) = 1/sin(θ)
cot(θ) = cos(θ)/sin(θ)
sec(θ) = 1/cos(θ)
sin²(θ) + cos²(θ) = 1

Theorems

Pythagorean identity

Suitable Grade Level

Grades 10-12