Jan 26Expression of the form a^2-b^2*x^2 : We make a sine substitutionSubstitute x=a/b*sin(θ) (-π/2≤θ≤π/2) so d(x)=a/b*cos(θ)*d(θ) and then √(,a^2-b^2*x^2)=√(,a^2-b^2*(a/b*sin(θ))^2)=√(,a^2-a^2*sin^2(θ))=a√(,1-sin^2(θ)) =a√(,cos^2(θ))=a*cos(θ)