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Chapter 2: Differentiation. L2.5 Implicit Differentiation. Day 1 Warm up. Find dy/dx : a) b) 5x 2 – 3y = x + 10 for both a) and b) since they are the same equation!
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Chapter 2: Differentiation L2.5 Implicit Differentiation
Day 1 Warm up Find dy/dx: a) b) 5x2 – 3y = x + 10 for both a) and b) since they are the same equation! When we have y on left and x’s on right, we find dy/dx using explicit differentiation.
Implicit Differentiation When we can’t write y = ‘some fcn of x’, we use implicit differentiation, with the Chain Rule. Implicit Differentiation: • Differentiate both sides with respect to x. If term has a y in it, take derivative of y and multiply by dy/dx (from Chain Rule). • Collect terms with dy/dx on one side and factor out dy/dx. • Solve to get dy/dx = ….
Implicit Differentiation Find . • y3 + y2 – 5y – x2 = −4 • From today’s warm up, we saw that dy/dx was the same for and 5x2 – 3y = x + 10 because they are the same equation. Find dy/dxusing implicit differentiation on the 2nd equation. Do you get the same result?? 3. x2y + xy2 = 6 4. See handout for other examples
Warm up Find the slope of the tangent line at the point (3,4) on the semicircle: A circle is the union of two differentiable functions. x2 + y2 = 25 → There are two ways to get the slope of a tangent: • Break into separate functions and find explicit derivative of each. • Use implicit differentiation – get derivative of whole thing at once. Exercises: Find slope of tangent line for • x2 + 4y2 = 4 at 2. y4 = y2 – x2 at
Implicit Differentiation Given sin y = x. Find dy/dx. Can you write dy/dx in terms of just x? Often the form of the derivative can be simplified by using the original equation or a prior derivative. Find if 2x3 − 3y2 = 8.