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

    0
    ReputationRep:
    I have been doing some C4 practice papers and there is the one question that I cannot get the right answer for.

    Find the value of f'(x) at the value x=Pi/3 for f(x)=tan2xsinx

    Now, I can get so far as getting f'(x) and according to the answer booklet it is correct at f'(x)=2.sec^2.2x.sinx + tan2x.cosx but when I substitute in Pi/3 I keep coming up with a wrong answer.

    Please could someone help. Thank you
    Offline

    2
    ReputationRep:
    f'(x)=2.sec^2.2x.sinx + tan2x.cosx when x=pi/3
    = 2 x 4 x 0.866 + -1.732 x 0.5
    =6.928 - 0.866
    =6.06 (3sf)

    Is this either of the answers you have?
    Offline

    1
    ReputationRep:
    r u sure u set ur calculator on "radians"?
    Offline

    15
    ReputationRep:
    (Original post by franks)
    f'(x)=2.sec^2.2x.sinx + tan2x.cosx when x=pi/3
    = 2 x 4 x 0.866 + -1.732 x 0.5
    =6.928 - 0.866
    =6.06 (3sf)

    Is this either of the answers you have?
    Seems to be correct
    • Thread Starter
    Offline

    0
    ReputationRep:
    Yes that is what I have been getting but the answers at the back say that it is wrong. Nevermind, I will put it as that. Thank you.
    Offline

    15
    ReputationRep:
    (Original post by BS-E-M-Student)
    Yes that is what I have been getting but the answers at the back say that it is wrong. Nevermind, I will put it as that. Thank you.
    What is their answer?
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: April 14, 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.