Area Between Curves Math Example 3

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Example 3

easy
Find the area between y=4โˆ’x2y = 4-x^2 and the xx-axis where the parabola is above the axis.

Solution

  1. 1
    Zeros: x=ยฑ2x = \pm 2. Parabola is above xx-axis on [โˆ’2,2][-2,2].
  2. 2
    A=โˆซโˆ’22(4โˆ’x2)โ€‰dx=[4xโˆ’x33]โˆ’22=(8โˆ’83)โˆ’(โˆ’8+83)=323A = \int_{-2}^{2}(4-x^2)\,dx = \left[4x-\frac{x^3}{3}\right]_{-2}^{2} = (8-\frac{8}{3})-(-8+\frac{8}{3}) = \frac{32}{3}.

Answer

323\frac{32}{3}
The parabola opens downward, is above the axis between x=ยฑ2x = \pm 2. Integrate the function directly over that interval.

About Area Between Curves

The area of the region enclosed between two functions f(x)f(x) and g(x)g(x) from x=ax = a to x=bx = b, computed as A=โˆซabโˆฃf(x)โˆ’g(x)โˆฃโ€‰dxA = \int_a^b |f(x) - g(x)|\,dx.

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