Derivative Rules and Applications
Derivatives tell us the rate at which functions change. Learning the basic derivative rules will make calculus much easier! The most common rules include power rule $x^n → nx^{n-1}$, trigonometric functions like sinx→cosx, and ex→ex (the only function that's its own derivative!).
When functions get more complex, we use special techniques. The product rule helps with multiplied functions $f·g → f·g' + g·f'$, the quotient rule works for divided functions $\frac{f}{g} → \frac{g·f' - f·g'}{g^2}$, and the chain rule handles composite functions ($f(g(x)) → f'(g(x))·g'(x)$).
Let's see these rules in action! For f(x)=4x5−5x4, we get f′(x)=20x4−20x3 using the power rule. With f(x)=exsinx, we apply the product rule to get f′(x)=exsinx+excosx.
💡 When differentiating, think about which rule fits the situation. Is it a product of functions? Use the product rule. A function inside another function? That's the chain rule!