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3-9 Continued & Review. Miss Battaglia BC Calculus. Definition of Differentials. Let y=f(x) represent a functions that is differentiable on an open interval containing x. The differential of x (denoted by dx) is any nonzero real number. The differential of y (denoted dy ) is
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3-9 Continued & Review Miss Battaglia BC Calculus
Definition of Differentials Let y=f(x) represent a functions that is differentiable on an open interval containing x. The differential of x (denoted by dx) is any nonzero real number. The differential of y(denoted dy) is dy = f’(x) dx -dy is the change in y -dx is the change in x -delta y pick a point close to point as limit approaches 0 dy/dx is the change in y over change in x! Δy dy
Comparing Δy and dy Let y=x2. Find dy when x=1 and dx=0.01. Compare this value with Δy for x=1 and Δx=0.01. Δy dy
Error Propagation The measured value x is used to compute another value f(x), the difference between f(x+Δx) and f(x) is the propagated error. f(x + Δx) – f(x) = Δy Measurement Error Propagated Error MeasuredValue Exact Value
Estimation of Error The measurement radius of a ball bearing is 0.7 in. If the measurement is correct to within 0.01 in, estimate the propagated error in the volume V of the ball bearing.
Differential Formulas Each of the differential rules from Chapter 2 can be written in differential form. Let u and v be differentiable functions of x. Constant multiple: d[cu] = c du Sum or difference: d[u + v] = du + dv Product: d[uv] = udv + vdu Quotient: d[u/v] =
Finding the Differential of a Composite Function y = f(x) = sin 3x
Finding the Differential of a Composite Function y = f(x) = (x2 + 1)1/2
Differentials can be used to approximate function values. To do this for the function given by y=f(x), use the formula f(x + Δx) = f(x) + dy = f(x) + f’(x)dy
Approximating Function Values Use differentials to approximate
Optimization A window is being built and the bottom is a rectangle and the top is a semicircle. If there is 12 meters of framing materials what must the dimensions of the window be to let in the most light?
Rectilinear Motion Example: s(t) = 2t3 – 21t2 + 60t + 3, 0 < t < 8 • Describe the motion of the particle with a calculator.
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