Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 2 - Section 2.1 - Definition II: Right Triangle Trigonometry - 2.1 Problem Set: 30


$(90-y)^{\circ}$ $ \sin y^{\circ} = \cos (90-y)^{\circ}$

Work Step by Step

Using Cofunction Theorem- $ \sin y^{\circ} = \cos (90-y)^{\circ}$ Reason- sine and cosine are cofunctions and $ y^{\circ} + (90-y)^{\circ} = 90^{\circ}$ i.e. $ y^{\circ}$ and $ (90-y)^{\circ}$ are complementary angles.
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