Question

If cos(x)=-5/13, and x satisfies 0 14 years ago

Answer 1

i think you just did this exact problem
\[\cos(x)=-\frac{5}{13}\]
\[\sin(x)=\frac{12}{13}\] and now double angle formulas

Answer 2

i.e., cos 2x = cos^2 x - sin^2 x
sin 2x = 2 sin x . cos x
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