Algebra and Trigonometry 10th Edition

Published by Cengage Learning
ISBN 10: 9781337271172
ISBN 13: 978-1-33727-117-2

Chapter 7 - 7.4 - Sum and Difference Formulas - 7.4 Exercises - Page 538: 30



Work Step by Step

$cos(u+v)=cos~u~cos~v-sin~u~sin~v$ $cos~130°~cos~40°-sin~130°~sin~40°=cos(130°+40°)=cos~170°$
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