Differentiable
If limit exists
We say that f is differentiable at x = a
Derivative of f(a)
f(a + h) - f(a) f(x) - f(a)
lim —————– = lim ————–
h->0 h x-> a x - a
Tangent line in point-slope form
y - f(a) = f’(a) (x-a)
To calculate f’(a) using the limit definition
Power rule
d
— x^n = nx^(n-1)
dx
Sum rule
(f + g)’ = f’ + g’
Constant multiple rule
(cf)’ = cf’
d
— e^x
dx
e^x
Differentiability implies continuity
However, there exist continuous functions that aren’t differentiable