Given Integral: We are given the integral to evaluate:∫−22(x3cos(2x)+21)4−x2dxFirst, we notice that the function has a square root of 4−x2, which suggests a trigonometric substitution might be useful. However, before we proceed with any substitution, let's examine the integrand for any symmetry properties that might simplify the calculation.
Symmetry Properties: We observe that the function x3cos(2x) is an odd function because replacing x with −x changes the sign of the function, and the function 4−x2 is even because replacing x with −x does not change the value of the function. The product of an odd function and an even function is an odd function. The term 21 is a constant and does not affect the symmetry of the first term.Since the integral is over a symmetric interval from −2 to 2, the integral of the odd function part will be zero. Therefore, we only need to evaluate the integral of the constant term (21) multiplied by 4−x2.
Evaluate Remaining Term: Now we evaluate the integral of the remaining term: ∫−22214−x2dxThis integral represents the area of a semicircle with radius 2, because the function 4−x2 describes a semicircle. The area of a full circle with radius r is πr2, so the area of a semicircle is 21πr2.
Calculate Semicircle Area: We calculate the area of the semicircle with radius 2: Area = (1/2)π(2)2=(1/2)π(4)=2πThis is the value of the integral of the constant term (1/2) multiplied by 4−x2 from −2 to 2.
Final Integral Value: Therefore, the value of the original integral is also 2π, since the integral of the odd function part is zero.
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