The Student Room Group

Differentiating parametric equations help :(

x=4cos2t,y=3sint x = 4cos2t, y = 3sint

Find dy/dx...ive done this but the book says im wrong:

dydx=dydt×dtdx \frac{dy}{dx} = \frac{dy}{dt} \times \frac{dt}{dx}

dydt=3cost \frac{dy}{dt} = 3cost

dtdx=1dxdt=18sin2t \frac{dt}{dx} = \frac{1}{\frac{dx}{dt}} = \frac{1}{-8sin2t}

Unparseable latex formula:

\frac{dy}[dx} = 3cost \times \frac{1}{-8sin2t}



=3cost8sin2t = \frac{3cost}{-8sin2t}

However the book says:

316cosect \frac{-3}{16}cosect

Please help!

Thanks
Reply 1


Uploaded with ImageShack.us

Quick Reply

Latest