Math Problem Statement

Assume that θ is the measure of an angle in Quadrant II satisfying csc(θ) = 3 2 . (a) Give a rough sketch showing the angle in a unit or non-unit circle in the coordinate plane (your choice). (b) Find the values of all the other five trigonometric functions at θ. Support your answers by showing your work in the space below.

Solution

Part (a): Rough Sketch

To visualize the angle θ\theta in Quadrant II with csc(θ)=32\csc(\theta) = \frac{3}{2}, let's go through the steps:

  1. The cosecant function is the reciprocal of the sine function. So, we have:

csc(θ)=1sin(θ)\csc(\theta) = \frac{1}{\sin(\theta)}

Since csc(θ)=32\csc(\theta) = \frac{3}{2}, it follows that:

sin(θ)=23\sin(\theta) = \frac{2}{3}

  1. In Quadrant II, the sine function is positive, and the cosine function is negative.

  2. Now, using the Pythagorean identity:

sin2(θ)+cos2(θ)=1\sin^2(\theta) + \cos^2(\theta) = 1

Substitute sin(θ)=23\sin(\theta) = \frac{2}{3}:

(23)2+cos2(θ)=1\left(\frac{2}{3}\right)^2 + \cos^2(\theta) = 1

49+cos2(θ)=1\frac{4}{9} + \cos^2(\theta) = 1

cos2(θ)=149=59\cos^2(\theta) = 1 - \frac{4}{9} = \frac{5}{9}

cos(θ)=53\cos(\theta) = -\frac{\sqrt{5}}{3}

Since we are in Quadrant II, cos(θ)\cos(\theta) is negative.

  1. The other trigonometric functions can be derived from the sine and cosine values.

Part (b): Find the Values of All Six Trigonometric Functions

  1. Sine: sin(θ)=23\sin(\theta) = \frac{2}{3}

  2. Cosine: cos(θ)=53\cos(\theta) = -\frac{\sqrt{5}}{3}

  3. Tangent: tan(θ)=sin(θ)cos(θ)=2353=25=255\tan(\theta) = \frac{\sin(\theta)}{\cos(\theta)} = \frac{\frac{2}{3}}{-\frac{\sqrt{5}}{3}} = -\frac{2}{\sqrt{5}} = -\frac{2\sqrt{5}}{5}

  4. Secant (reciprocal of cosine): sec(θ)=1cos(θ)=153=35=355\sec(\theta) = \frac{1}{\cos(\theta)} = \frac{1}{-\frac{\sqrt{5}}{3}} = -\frac{3}{\sqrt{5}} = -\frac{3\sqrt{5}}{5}

  5. Cosecant (reciprocal of sine): csc(θ)=1sin(θ)=123=32\csc(\theta) = \frac{1}{\sin(\theta)} = \frac{1}{\frac{2}{3}} = \frac{3}{2}


Final Trigonometric Values:

  1. sin(θ)=23\sin(\theta) = \frac{2}{3}
  2. cos(θ)=53\cos(\theta) = -\frac{\sqrt{5}}{3}
  3. tan(θ)=255\tan(\theta) = -\frac{2\sqrt{5}}{5}
  4. sec(θ)=355\sec(\theta) = -\frac{3\sqrt{5}}{5}
  5. csc(θ)=32\csc(\theta) = \frac{3}{2}

Questions for Further Study:

  1. How do the signs of trigonometric functions change in different quadrants?
  2. Can we calculate the trigonometric functions for angles in other quadrants if we know the values of sine or cosine?
  3. What is the significance of using Pythagorean identities in trigonometry?
  4. How do reciprocal trigonometric functions relate to each other in terms of sine, cosine, and tangent?
  5. What are some methods to quickly determine the values of sine, cosine, and tangent for special angles?

Tip: Remember that the trigonometric functions are periodic, so knowing one cycle of these functions helps to find their values for other angles that differ by multiples of 2π2\pi.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Trigonometric Functions
Unit Circle
Pythagorean Identity

Formulas

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

Theorems

Pythagorean Identity

Suitable Grade Level

Grades 10-12