Question

How many values of x are there if sinx=5/7?

Answer 1

Following are the values of x ;

If Sin x = 5/7, 
cosx=√1−(57)2
=√247=2√67
Then,
sin2x=2sinx⋅cosx
=2⋅57⋅√247
=20√649

Then, 
cos2x= ⎷1−(20√649)2
=√2401−24002401
=149

Then, since
tan(2x)=sin(2x)cos(2x)
tan(2x)=20√6