If tan ( x ) = 18/13 (in Quadrant-I), find sin ( 2 x )

Answer 1

There's a formula for sin(2x), In fact, it's a direct consequence of the formula for the sine of the sum of 2 angles.

sin(A+B) = sin(A)cos(B) + cos(A)sin(B)

Just set A = B in the formula and you will have it!