The right triangle CDE calculates DE=2.
The angle CED=60 degrees is calculated by Pythagorean theorem.
So calling AED is equal to 90 degrees.
AD= root number (DE square +AE square) = root number (4+3)= root number 7.
Take b as AE foot, and the square of AE is calculated as 3.
The answer is the root number 7.