\($\sin A = 2\cos A$\)
Note that cos A ≠ 0 ( A would have to be 90°....but we know that B = 90°)
So we have that
sin A / cos A = 2
tan A = 2
Which implies that
y = 2 and x =1
r = sqrt [ 1^2 + 2^2 ] =sqrt 5
So
cos A = x / r = 1 / sqrt 5 = sqrt (5) / 5
