If #sin B = -12/13# then what is #cos 2B# ?
2 Answers
Explanation:
Once you have worked out the value of
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Explanation:
Given:
#sin B = -12/13#
Then:
#cos 2B = 2 cos^2 B - 1#
#color(white)(cos 2B) = 2(1-sin^2 B) - 1#
#color(white)(cos 2B) = 1-2 sin^2 B#
#color(white)(cos 2B) = 1-2 (-12/13)^2#
#color(white)(cos 2B) = 1-288/169#
#color(white)(cos 2B) = (169-288)/169#
#color(white)(cos 2B) = -119/169#