变限积分求导

$$\int _a ^x f(t)dt = f(x)$$ $$\int _x ^a f(t)dt = -f(x)$$ $$\int _{a} ^{\psi(x)} f(t)dt = \psi{'}{(x)}f[(\psi(x)]$$ $$\int _{\psi(x)} ^{a} f(t)dt = -\psi{'}{(x)}f[(\psi(x)]$$