Q. A curve is defined by the parametric equations x(t)=−6sin(−9t) and y(t)=4cos(4t). Find dxdy.Answer:
Find dtdx: To find dxdy for parametric equations, we need to find dtdy and dtdx separately and then divide dtdy by dtdx.
Find dtdy: First, we find dtdx. The derivative of x(t)=−6sin(−9t) with respect to t is dtdx=−6×−9×cos(−9t)=54cos(−9t), because the derivative of sin(u) with respect to u is cos(u) and we apply the chain rule for the derivative of −9t.
Divide to find dxdy: Next, we find dtdy. The derivative of y(t)=4cos(4t) with respect to t is dtdy=−4×4×sin(4t)=−16sin(4t), because the derivative of cos(u) with respect to u is −sin(u) and we apply the chain rule for the derivative of 4t.
Simplify the expression: Now we divide dtdy by dtdx to find dxdy. So, dxdy=54cos(−9t)−16sin(4t).
Simplify the expression: Now we divide dtdy by dtdx to find dxdy. So, dxdy=54cos(−9t)−16sin(4t).We can simplify the expression by dividing both the numerator and the denominator by 2, which gives us dxdy=27cos(−9t)−8sin(4t).
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