Q. Given that x=4w2+4, find dwd(x4−5sinw) in terms of only w.Answer:
Expand x4: First, we need to express x4−5sin(w) in terms of w using the given expression for x. We have x=4w2+4. To find x4, we need to raise the expression for x to the fourth power.
Calculate x4: We calculate x4 by raising (4w2+4) to the fourth power. This involves expanding the binomial (4w2+4)4 using the binomial theorem or by multiplying the expression by itself four times. However, since we are ultimately interested in the derivative with respect to w, we can simplify our work by differentiating directly without fully expanding the binomial.
Chain rule for x4: The derivative of x4 with respect to w can be found using the chain rule. The chain rule states that the derivative of a composite function is the derivative of the outer function evaluated at the inner function times the derivative of the inner function. In this case, the outer function is u4 (where u=x) and the inner function is x(w)=4w2+4.
Combine derivatives: Using the chain rule, we differentiate x4 with respect to x and then multiply by the derivative of x with respect to w. The derivative of x4 with respect to x is 4x3. The derivative of x with respect to w is the derivative of 4w2+4, which is x0.
Differentiate −5sin(w): Now we combine the two derivatives to find the derivative of x4 with respect to w: (dwd)(x4)=4x3∗(dwd)(x)=4x3∗8w=32wx3.
Sum of derivatives: Next, we need to differentiate −5sin(w) with respect to w. The derivative of −5sin(w) with respect to w is −5cos(w).
Substitute x into derivative: We now have the derivatives of both terms in the expression x4−5sin(w). The derivative of the entire expression with respect to w is the sum of the derivatives of the individual terms: (dwd)(x4−5sin(w))=32wx3−5cos(w).
Substitute x into derivative: We now have the derivatives of both terms in the expression x4−5sin(w). The derivative of the entire expression with respect to w is the sum of the derivatives of the individual terms: (d/dw)(x4−5sin(w))=32wx3−5cos(w).Finally, we substitute x=4w2+4 into the expression for the derivative to express it entirely in terms of w: (d/dw)(x4−5sin(w))=32w(4w2+4)3−5cos(w).
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