The given triangle is a 30°- 60°- 90° triangle.

Here  is the hypotenuse , is the shorter leg, and  is the longer leg.

The 30°- 60°- 90° triangle has the property that the length of its hypotenuse is

twise the length of the shorter leg, and the length of the longer leg is times

to the length of the shorter leg..

                  (Substitute )

                        (Divide each side by 2)

              (Substitute a = 4)

                 (Multiply)

The value of a is 4 and b is 6.92.