Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    Hello, I was wondering if anyone could help me. I'm struggling with parametric equations with trig fuctions, but i think the root of it is that I cant seem to do trig equations anymore.

    I have this questions which i have the wrong answer to so if anyone could tell me where im going wrong i would appriciate it.

    1) A curve is defined by the parametric equations:

    x = 3 + sin2t y = 8t + 4cos2t

    a) Show that at the point Q, where t=0, the gradient of the curve is 4.

    So firstly I did dx/dt = cos2t and then i did dy/dt = -4sin2t

    So for dy/dx I got: -4sin2t/cos2t

    So when i put t=0 into my calculator i got 0/0 = 0 hence i dont understand where im going wrong.

    Can anyone help?

    Thanks.
    Offline

    16
    ReputationRep:
    (Original post by KaosLisa)
    Hello, I was wondering if anyone could help me. I'm struggling with parametric equations with trig fuctions, but i think the root of it is that I cant seem to do trig equations anymore.

    I have this questions which i have the wrong answer to so if anyone could tell me where im going wrong i would appriciate it.

    1) A curve is defined by the parametric equations:

    x = 3 + sin2t y = 8t + 4cos2t

    a) Show that at the point Q, where t=0, the gradient of the curve is 4.

    So firstly I did dx/dt = cos2t and then i did dy/dt = -4sin2t

    So for dy/dx I got: -4sin2t/cos2t

    So when i put t=0 into my calculator i got 0/0 = 0 hence i dont understand where im going wrong.

    Can anyone help?

    Thanks.
    Your differentiation is wrong.
    dx/dt = 2cos2t
    dy/dt = 8 - 8sin2t

    dy/dx = dy/dt x 1/dx/dt
    dy/dx = (8-8sin2t)/2cos2t

    When t = 0
    dy/dx = (8-8sin0)/2cos0 = (8-0)/2 = 4
    • Thread Starter
    Offline

    0
    ReputationRep:
    Ah got it now thank you!
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: April 12, 2006
Poll
Do you agree with the proposed ban on plastic straws and cotton buds?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.