Question

if sinAcosA = 6/13 find the value of CosA​

Answer 1

sinAcosA = 6/13

$\frac{ \sin(2a) }{2} = \frac{6}{13} \\ \sin(2a) = \frac{12}{13} \\ \cos(2a) = \frac{25}{13 } \\ 2 \cos^{2} (a) - 1 = \frac{25 }{13} \\ \cos^{2} (a) = \frac{19}{13} \\ \cos(a) = \sqrt{ \frac{19}{13} }$