Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 5 - Trigonometric Identities - Section 5.1 Fundamental Identities - 5.1 Exercises - Page 195: 54

Answer

$$\cot x=\pm\frac{\sqrt{1-\sin^2 x}}{\sin x}$$

Work Step by Step

According to Pythagorean Identities, $$\cot^2x+1=\csc^2 x\hspace{1.5cm}(1)$$ Also, according to Reciprocal Identities, $$\csc x=\frac{1}{\sin x}$$ So, $$\csc^2 x=\frac{1}{\sin^2 x}\hspace{1.5cm}(2)$$ We can combine $(1)$ and $(2)$ together and have $$\cot^2 x+1=\frac{1}{\sin^2 x}$$ $$\cot^2 x=\frac{1}{\sin^2 x}-1$$ $$\cot^2 x=\frac{1-\sin^2 x}{\sin^2 x}$$ Now we take the square root of both sides: $$\cot x=\pm\frac{\sqrt{1-\sin^2 x}}{\sqrt{\sin^2 x}}$$ (Do not forget the $\pm$ sign) $$\cot x=\pm\frac{\sqrt{1-\sin^2 x}}{|\sin x|}$$ Since we already have the $\pm$ sign, we can eliminate the absolute value sign. $$\cot x=\pm\frac{\sqrt{1-\sin^2 x}}{\sin x}$$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.