Q. A curve is defined by the parametric equations x(t)=−7cos(−6t) and y(t)=9sin(6t). 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)=−7cos(−6t) with respect to t is dtdx=−7×6sin(−6t) because the derivative of cos(u) with respect to u is −sin(u) and we apply the chain rule with u=−6t. dtdx=−7×6sin(−6t)=42sin(−6t)
Calculate dxdy: Next, we find dtdy. The derivative of y(t)=9sin(6t) with respect to t is dtdy=9×6cos(6t) because the derivative of sin(u) with respect to u is cos(u) and we apply the chain rule with u=6t. dtdy=9×6cos(6t)=54cos(6t)
Simplify fraction: Now we divide dtdy by dtdx to find dxdy.dxdy=dtdxdtdy=42sin(−6t)54cos(6t)
Final result: We can simplify the fraction by dividing both the numerator and the denominator by 6. dxdy=(642⋅sin(−6t))(654⋅cos(6t))=(7sin(−6t))(9cos(6t))
Final result: We can simplify the fraction by dividing both the numerator and the denominator by 6. dxdy=(42/6⋅sin(−6t))(54/6⋅cos(6t))=(7sin(−6t))(9cos(6t))Since sin(−θ)=−sin(θ), we can simplify the denominator to −sin(6t). dxdy=(7⋅−sin(6t))(9cos(6t))=−7sin(6t)9cos(6t)
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