find sin2x, cos2x, and tan2x if sinx= -1/sqrt 5 and x terminates in quadrant II

Answer 1

sorry. sinx is not negative in QII.
But draw your triangle. Recall that
sinx = y/r
cosx = x/r
Then just apply your double angle formulas.
Assuming that you meant QIII, then you have
cosx = -2/√5
sin2x = 2sinx cosx = 2(-1/√5)(-2/√5) = 4/5
and so on for the other functions.