The angle α verifies 90° < α < 180° and sin(α) = 12/13. Without using the trigonometric keys of the calculator, determine the exact and simplified values of cos(α) and sin(α + 45°). Many thanks for helping me!
Added by Jose Ramon M.
Step 1
We know that sin(alpha) = 12/13, so we can use the Pythagorean identity to find cos(alpha): cos^2(alpha) + sin^2(alpha) = 1 cos^2(alpha) + (12/13)^2 = 1 cos^2(alpha) = 1 - (12/13)^2 cos^2(alpha) = 25/169 cos(alpha) = ±5/13 Note that we have two possible values Show more…
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