# What is the integral of sqrt(1-x^2)?

Hint: First, apply trigonometric substitution. This question is in the form $\sqrt{{a}^{2} - {x}^{2}}$. So you let x = a sinx (a in this case is 1) then take the derivative of x. Plug it back in the question $\int \sqrt{1 - {x}^{2}} \mathrm{dx}$