Q. A curve is defined by the parametric equations x(t)=−3cos(−t) and y(t)=5e−9t. 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, let's find dtdx. The derivative of x(t)=−3cos(−t) with respect to t is dtdx=−3⋅dtd[cos(−t)]. Since the derivative of cos(u) with respect to u is −sin(u), and using the chain rule with u=−t, we get dtdx=−3⋅(−sin(−t))⋅(−1)=3sin(−t).
Calculate dxdy: Now, let's find dtdy. The derivative of y(t)=5e−9t with respect to t is dtdy=5⋅dtd[e−9t]. Since the derivative of eu with respect to u is eu, and using the chain rule with u=−9t, we get dtdy=5⋅e−9t⋅(−9)=−45e−9t.
Simplify dxdy: To find dxdy, we divide dtdy by dtdx. So, dxdy=dtdxdtdy=3sin(−t)−45e−9t.
Simplify dxdy: To find dxdy, we divide dtdy by dtdx. So, dxdy=dtdxdtdy=3sin(−t)−45e−9t.We can simplify the expression for dxdy by dividing both the numerator and the denominator by 3. This gives us dxdy=sin(−t)−45/3e−9t=−15e−9t/sin(−t).
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