You are Here: Home >< Maths

# Integration Question Solomon Help watch

1. https://5c59854d0ccd29d489c9e5e689a8...%20Edexcel.pdf

Q7c I cant see why you need to multiply cosec(t) by the derivative of cos(2t)
2. (Original post by Sniperdon227)
https://5c59854d0ccd29d489c9e5e689a8...%20Edexcel.pdf

Q7c I cant see why you need to multiply cosec(t) by the derivative of cos(2t)
you want the integral of y with respect to x, not to t.
thus dx/dt = -2sin2t -> dx = -2 sin 2t dt.
Hence we require the integral of cosec t * -2 * 2 sin t cos t dt, i.e. integral of -4 cos t dt (since cosec t and sin t cancel out), so k = -4.
3. (Original post by Sniperdon227)
https://5c59854d0ccd29d489c9e5e689a8...%20Edexcel.pdf

Q7c I cant see why you need to multiply cosec(t) by the derivative of cos(2t)
Because you integrate in cartesian which is the same as in parametric. So to get the as required in the answer you need to compensate by multiplying by the derivative of with respect to . It is not true that .
4. Thanks i get it now, learnt something new
5. (Original post by Sniperdon227)
Thanks i get it now, learnt something new
Great! No problem.
6. (Original post by HapaxOromenon3)
you want the integral of y with respect to x, not to t.
thus dx/dt = -2sin2t -> dx = -2 sin 2t dt.
Hence we require the integral of cosec t * -2 * 2 sin t cos t dt, i.e. integral of -4 cos t dt (since cosec t and sin t cancel out), so k = -4.
Isnt k=4 because they swapped the limits around?
7. (Original post by metrize)
Isnt k=4 because they swapped the limits around?
MS:
correct the limits switch, only because of the minus sign and because it wants you to
https://5c59854d0ccd29d489c9e5e689a8...%20Edexcel.pdf

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: June 6, 2016
Today on TSR

### Edexcel C3 Maths Unofficial Markscheme

Find out how you've done here

### 1,115

students online now

Exam discussions

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams