If cosA = 3/5, 0deg <A<90deg write sinA as a fraction. Hence write cos2A as a fraction. I've got the first part sinA as a fraction, 4/5 . The second part, cos2A as a fraction is getting me. Any help?
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Originally Posted by zyx.gar If cosA = 3/5, 0deg <A<90deg write sinA as a fraction. Hence write cos2A as a fraction. I've got the first part sinA as a fraction, 4/5 . The second part, cos2A as a fraction is getting me. Any help? Hi zyx.gar, Try using the double angle identity:
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