Integration and the Fundamental Theorem

Integrate functions and apply the fundamental theorem of calculus for IB Maths.

Integration reverses differentiation and computes areas. The fundamental theorem of calculus connects the two.

Standard Integrals

xndx=xn+1n+1+C\int x^n\,dx = \frac{x^{n+1}}{n+1} + C (n1n \neq -1)

1xdx=lnx+C\int \frac{1}{x}\,dx = \ln|x| + C, exdx=ex+C\int e^x\,dx = e^x + C

sinxdx=cosx+C\int \sin x\,dx = -\cos x + C, cosxdx=sinx+C\int \cos x\,dx = \sin x + C

Fundamental Theorem

abf(x)dx=F(b)F(a)\int_a^b f(x)\,dx = F(b) - F(a)

where F(x)=f(x)F'(x) = f(x).

Area Between Curve and x-axis

Area=abf(x)dx\text{Area} = \int_a^b |f(x)|\,dx. Split at roots if f(x)f(x) changes sign.

Worked Example

13(2x+1)dx=[x2+x]13=(9+3)(1+1)=10\int_1^3 (2x + 1)\,dx = [x^2 + x]_1^3 = (9+3) - (1+1) = 10.

Practice Problems

    1. (3x22x+1)dx\int (3x^2 - 2x + 1)\,dx.
    1. 0πsinxdx\int_0^{\pi} \sin x\,dx.
    1. Find the area between y=x24y = x^2 - 4 and the x-axis from x=0x = 0 to x=3x = 3.

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Key Takeaways

  • Integration reverses differentiation (+ constant CC).

  • Definite integral: F(b)F(a)F(b) - F(a).

  • Area below x-axis must be taken as positive.

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