Find a polar equation for the curve represented by the given Cartesian equation .
Table of contents
- 0. Review of College Algebra4h 45m
- 1. Measuring Angles40m
- 2. Trigonometric Functions on Right Triangles2h 5m
- 3. Unit Circle1h 19m
- 4. Graphing Trigonometric Functions1h 19m
- 5. Inverse Trigonometric Functions and Basic Trigonometric Equations1h 41m
- 6. Trigonometric Identities and More Equations2h 34m
- 7. Non-Right Triangles1h 38m
- 8. Vectors2h 25m
- 9. Polar Equations2h 5m
- 10. Parametric Equations1h 6m
- 11. Graphing Complex Numbers1h 7m
3. Unit Circle
Defining the Unit Circle
Problem 11
Textbook Question
Suppose ABC is a right triangle with sides of lengths a, b, and c and right angle at C. Use the Pythagorean theorem to find the unknown side length. Then find exact values of the six trigonometric functions for angle B. Rationalize denominators when applicable. See Example 1.

a = 5, b = 12
Verified step by step guidance1
Identify the sides of the right triangle ABC, where the right angle is at C. This means sides a and b are the legs, and side c is the hypotenuse opposite the right angle.
Use the Pythagorean theorem to find the length of the hypotenuse c: \(c^2 = a^2 + b^2\). Substitute the given values: \(c^2 = 5^2 + 12^2\).
Calculate \(c^2\) by squaring the given sides: \(c^2 = 25 + 144\). Then express \(c\) as \(c = \sqrt{169}\), but do not simplify further here.
To find the six trigonometric functions for angle B, first identify the sides relative to angle B: the side opposite B is a, the side adjacent to B is b, and the hypotenuse is c.
Write the six trigonometric functions in terms of a, b, and c:
- \(\sin B = \frac{\text{opposite}}{\text{hypotenuse}} = \frac{a}{c}\)
- \(\cos B = \frac{\text{adjacent}}{\text{hypotenuse}} = \frac{b}{c}\)
- \(\tan B = \frac{\text{opposite}}{\text{adjacent}} = \frac{a}{b}\)
- \(\csc B = \frac{1}{\sin B} = \frac{c}{a}\)
- \(\sec B = \frac{1}{\cos B} = \frac{c}{b}\)
- \(\cot B = \frac{1}{\tan B} = \frac{b}{a}\)
Substitute the known values for a, b, and c into these expressions and rationalize denominators if necessary.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Pythagorean Theorem
The Pythagorean theorem states that in a right triangle, the square of the hypotenuse (side opposite the right angle) equals the sum of the squares of the other two sides. It is expressed as c² = a² + b². This theorem allows you to find the missing side length when two sides are known.
Recommended video:
Solving Right Triangles with the Pythagorean Theorem
Trigonometric Functions
The six trigonometric functions—sine, cosine, tangent, cosecant, secant, and cotangent—relate the angles of a right triangle to the ratios of its sides. For an angle, these functions are defined using the lengths of the opposite, adjacent, and hypotenuse sides, providing exact values based on the triangle's dimensions.
Recommended video:
Introduction to Trigonometric Functions
Rationalizing Denominators
Rationalizing denominators involves rewriting a fraction so that its denominator contains no irrational numbers, such as square roots. This is done by multiplying numerator and denominator by a suitable radical to simplify expressions and present answers in a standard, exact form.
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Rationalizing Denominators
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