If x=sintcos2t and y=costsin2t, then at t=4π, the value of dxdy is equal to
(a) -2
(b) 2
(c) 21
(d) −21Intuitive explanation
The key is to find dxdy using the chain rule: dxdy=dx/dtdy/dt. You'll need to differentiate both x and y with respect to t using the product rule, then evaluate both derivatives at t=4π. The trigonometric values at this angle are simple (sin4π=cos4π=22), so the arithmetic becomes manageable once you've set up the derivatives correctly.
Intuitive explanation
The key is to find dxdy using the chain rule: dxdy=dx/dtdy/dt. You'll need to differentiate both x and y with respect to t using the product rule, then evaluate both derivatives at t=4π. The trigonometric values at this angle are simple (sin4π=cos4π=22), so the arithmetic becomes manageable once you've set up the derivatives correctly.