Answer
$\frac{\sqrt3-1}{2\sqrt2}$
Work Step by Step
Using the formula $\cos(A+B)=\cos A\cos B-\sin A\sin B$, I get: $\cos75=\cos30\cos45-\sin30\sin45=\frac{\sqrt3}{2}\frac{1}{\sqrt2}-0.5\frac{1}{\sqrt2}=\frac{\sqrt3-1}{2\sqrt2}$
Trigonometry 7th Edition
by McKeague, Charles P.; Turner, Mark D.
Published by
Cengage Learning
ISBN 10:
1111826854
ISBN 13:
978-1-11182-685-7
Chapter 8 - Section 8.2 - Trigonometric Form for Complex Numbers - 8.2 Problem Set - Page 433: 73
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