AP Calculus BC / Unit 6: Integration and Accumulation of Change
6.4 The Fundamental Theorem of Calculus and Accumulation Functions
Notes
For an accumulation function $\displaystyle g(x)=\int_a^x f(t)\,dt$:
$$g'(x)=f(x)$$
- With a variable upper limit $u(x)$: $\displaystyle \frac{d}{dx}\int_a^{u(x)}f(t)\,dt=f(u(x))\,u'(x)$.
Practice
$\displaystyle \frac{d}{dx}\int_2^x \cos(t^2)\,dt=$
FTC: plug $x$ into the integrand.
$\displaystyle \frac{d}{dx}\int_0^{x^3}\sqrt{1+t}\,dt=$
Chain rule with the upper limit $x^3$.
If $\displaystyle g(x)=\int_1^x f(t)\,dt$, then $g(1)=$
The integral from 1 to 1 is 0.
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