That is simply the area enclosed by the unit circle in the first quadrant.
How much is that?
Look at this page
Interpret the definite integrals as sums and differences of areas and then use simple geometric formulas to evaluate the integrals
Can somebody please help me with this one, I am not understanding how to approach it. I know it forms a fourth of a circle because of the bounds but that is all I am understanding.
IMHO x3bnm has shown very nicely how to work integrals using trigonometric substitutions. The OP asked for sums and differences of areas which x3bnm provided using simple geometric formulas of right triangles.
Surely an integral with trigonometric substitutions is much more difficult than . It's 100% correct and beautifully executed (and LaTeXed), but the question asked to use simple geometric formulas. Surely there are few more simple than the formula for the area of a circle...