Q. Given that x=3y3+1, find dyd(2x2−2cosy) in terms of only y.Answer:
Express Function in Terms of y: First, we need to express the function 2x2−2cos(y) in terms of y using the given relationship x=3y3+1. Substitute x=3y3+1 into the function to get a new function of y.
Substitute x into Function: The new function in terms of y is 2(3y3+1)2−2cos(y). Now we need to find the derivative of this new function with respect to y.
Find Derivative of New Function: To find the derivative, we will use the chain rule for the term 2(3y3+1)2 and the basic derivative rule for the term −2cos(y). The derivative of −2cos(y) with respect to y is 2sin(y).
Derivative of −2cos(y): Now, let's find the derivative of 2(3y3+1)2 with respect to y. Let u=3y3+1, then the term becomes 2u2. The derivative of 2u2 with respect to u is 4u.
Find Derivative of 2(3y3+1)2: Next, we need to find dydu, which is the derivative of u=3y3+1 with respect to y. The derivative of 3y3 with respect to y is 9y2, and the derivative of 1 with respect to y is 0. So, dydu0.
Find dydu: Now, we apply the chain rule. The derivative of 2u2 with respect to y is 4u⋅dydu. Substitute u=3y3+1 and dydu=9y2 into the equation to get 4(3y3+1)(9y2).
Apply Chain Rule: Simplify the expression 4(3y3+1)(9y2) to get 36y2(3y3+1).
Simplify Expression: Combine the derivatives of both terms to get the final derivative of the function with respect to y. The final derivative is 36y2(3y3+1)+2sin(y).
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