The angles of a triangle add up to 180. As one of the angles is 40 and it is a right triangle, the angles are 90, 40 and 50.
The hypotenuse is 10.
If the side opposite 40 degrees is S, sin 40 = S / 10
=> S = 6.427
Similarly the side opposite 50 degrees is 7.66
The angle and the side opposite them are 40, 6.427; 50, 7.66; 90, 10