# Derivation The derivative of a function gives us the slope of that function at a specific point. # Constant Derivatives Deriving any constant gives us a derivative of $x = 0$ $f(x) = 5$ $f'(x) = 0$ # Power Rule $\frac{d}{dx}(x^n) = nx^{(n-1)}$ $f(x) = x^2$ $f'(x) = x$ $f(x) = x^5$ $f'(x) = 5x^4$ You can also use the power rule to solve $f(x) = \frac{1}{x}$ $$ \begin{flalign} &f(x) = \frac{1}{x}&\\\ &f(x) = x^{-1}\\ &f('x) = -1x^{-1-1} = -1x^{-2} = \frac{-1x^{-2}}{1}\\ &f'(x) = \frac{-1}{x^2}\\ \end{flalign} $$ # Constant Multiple Rule The derivative of $constant * f(x)$ is $constant * f'(x)$. So we can see that the constant doesn't change. $f(x) = 5x^4$ $f'(x) = 5*4x^3 = 20x^3$ $f(x) = 8x^4$ $f'(x) = 32x^3$ $f(x) = 5x^6$ $f'(x) = 30x^5$ # Derive Radical Functions 🤘 $$ \begin{flalign} &f(x) = \sqrt{x}&\\\ &f(x) = \sqrt[2]{x^1}\\ &f(x) = x^{\frac{1}{2}}\\ &f'(x) = \frac{1}{2}x^{\frac{1}{2}-1} = \frac{1}{2}x^{-\frac{1}{²}}\\ &f'(x) = \frac{1x^{-\frac{1}{2}}}{2}\\ &f'(x) = \frac{1}{2x^{\frac{1}{2}}}\\ &f'(x) = \frac{1}{2\sqrt{x}} \end{flalign} $$ # Derive Sine/Cosine $\frac{d}{dx}[\sin{x}] = \cos{x}$ $\frac{d}{dx}[\cos{x}] = -\sin{x}$ # Product Rule This rule applies when you try to derive functions that are multiplied. $\frac{d}{dx}[f*x] = f'*g + f*g'$ # Example $$ \begin{flalign} &f(x) = x^3+7x^2-8x+6&\\\ &f'(x) = 3x^2+14x-8 \end{flalign} $$ $$ \begin{flalign} &f(x) = 4x^5+3x^4+9x+7&\\\ &f'(x) = 20x^4+12x^3+9 \end{flalign} $$ $$ \begin{flalign} &f(x) = 2x^5+5x^3+3x^2+4&\\\ &\text{Find the slope at } x = 2\\ &f'(x) = 10x^4+15x^2+6x\\ &f'(2) = 10(2)^4+15(2)^2+6(2)\\ &f'(2) = 232\\ \end{flalign} $$ $$ \begin{flalign} &f(x) = \frac{1}{x^2}&\\\ &f(x) = x^{-2}\\ &f'(x) = -2x^{-3}\\ &f'(x) = \frac{-2}{x^3n } \end{flalign} $$ $$ \begin{flalign} &f(x) = \sqrt[3]{x^5}&\\\ &f(x) = x^{\frac{5}{3}}\\ &f'(x) = \frac{5}{3}x^{\frac{2}{3}}\\ &f'(x) = \frac{5x^{\frac{2}{3}}}{3}\\ &f'(x) = \frac{5\sqrt[3]{x^2}}{3}\\ \end{flalign} $$ $$ \begin{flalign} &f(x) = \sqrt[7]{x^4}&\\\ &f(x) = x^{\frac{4}{7}}\\ &f'(x) = \frac{4}{7}x^{-\frac{3}{7}}\\ &f'(x) = \frac{4x^{-\frac{3}{7}}}{7}\\ &f'(x) = \frac{4}{7x^{\frac{3}{7}}}\\ &f'(x) = \frac{4}{7\sqrt[7]{x^3}} \end{flalign} $$ $$ \begin{flalign} &f(x) = (2x-3)^2&\\\ &f(x) = 4x^2-12x+9\\ &f'(x) = 8x - 12 \end{flalign} $$ $$ \begin{flalign} &f(x) = \frac{x^5+6x^4+5x^3}{x^2}&\\\ &f(x) = x^{-2}(x^5+6x^4+5x^3)\\ &f(x) = x^3+6x^2+5x\\ &f'(x) = 3x^2+12x+5 \end{flalign} $$