Turn on thread page Beta

More maths help because I seem to be an idiot right now watch

    • Thread Starter
    Offline

    8
    ReputationRep:
    Ok, so I was trying to do some work to prepare for A levels, but I keep getting the wrong answer to a certain question. I can't work out exactly where I have gone wrong, but I keep getting the answer of 8.01m when the answer sheet says that the answer is 7.52m. Could someone possibly give me a step by step method so that I can see exactly where I keep going wrong?

    The question is to find the value of x and this is the diagram: http://tinypic.com/view.php?pic=bi19w7&s=9#.WXjmw73TXqA
    Offline

    0
    ReputationRep:
    (Original post by Coco_Monkey)
    Ok, so I was trying to do some work to prepare for A levels, but I keep getting the wrong answer to a certain question. I can't work out exactly where I have gone wrong, but I keep getting the answer of 8.01m when the answer sheet says that the answer is 7.52m. Could someone possibly give me a step by step method so that I can see exactly where I keep going wrong?

    The question is to find the value of x and this is the diagram: http://tinypic.com/view.php?pic=bi19w7&s=9#.WXjmw73TXqA
    HOLD THE FOOK UP, are you doing a level work in the holidays?
    • Thread Starter
    Offline

    8
    ReputationRep:
    (Original post by sweet boner)
    HOLD THE FOOK UP, are you doing a level work in the holidays?
    Yes, one of the sixth forms that I applied to wants us to prepare for a test that there will be on the first week. So I'm doing some stuff in case I end up going there.
    Offline

    0
    ReputationRep:
    (Original post by Coco_Monkey)
    Yes, one of the sixth forms that I applied to wants us to prepare for a test that there will be on the first week. So I'm doing some stuff in case I end up going there.
    Ooooh good luck with the integration, trigonometric equations, Pythagorean identities and all that *******s
    you get the idea
    • Thread Starter
    Offline

    8
    ReputationRep:
    (Original post by sweet boner)
    Ooooh good luck with the integration, trigonometric equations, Pythagorean identities and all that *******s
    you get the idea
    Can't you help me?! And just looking at the names of those makes me want to cry a little on the inside
    Offline

    0
    ReputationRep:
    Can't you just use sine/cosine rule?
    Anyway, what do you think you got the maths gcse? I got around 125, is that a 6?
    Offline

    0
    ReputationRep:
    (Original post by Coco_Monkey)
    Can't you help me?! And just looking at the names of those makes me want to cry a little on the inside
    Just by looking at it, i say use pythag to find the hypotenuse.
    You know you have 1 right angle and 70 degree angle soo.....
    180- (70-90)= You get another angle then it's just easy work.
    • Thread Starter
    Offline

    8
    ReputationRep:
    (Original post by Vexillarius)
    Can't you just use sine/cosine rule?
    Anyway, what do you think you got the maths gcse? I got around 125, is that a 6?
    It's in the trigonometry section, so I'm guessing it wants me to use that. And I have no clue about grade boundaries
    Offline

    0
    ReputationRep:
    (Original post by Coco_Monkey)
    It's in the trigonometry section, so I'm guessing it wants me to use that. And I have no clue about grade boundaries
    Btw, sine and cosine rule are both uses of trigonometry AFAIK.
    • Thread Starter
    Offline

    8
    ReputationRep:
    (Original post by Vexillarius)
    Btw, sine and cosine rule are both uses of trigonometry AFAIK.
    I meant the whole sin, cos, tan area because that is the only stuff mentioned in the lesson part of the sheet.
    Online

    21
    ReputationRep:
    (Original post by Coco_Monkey)
    It's in the trigonometry section, so I'm guessing it wants me to use that. And I have no clue about grade boundaries
    Calculate the hypotenuse (y) of the 60 degree triangle. That is the opposite for the 70 degree triangle.

    cos(60)=\frac{11}{y}

    \therefore y=\frac{11}{cos(60)}

    For the second triangle, you have the opposite (y) and the adjacent (x). Using tan(70) you should be able to calculate x.
    Offline

    22
    ReputationRep:
    (Original post by Coco_Monkey)
    I meant the whole sin, cos, tan area because that is the only stuff mentioned in the lesson part of the sheet.
    In the left/up triangle, you can find the length of its hypotenuse by noting that \cos 60^{\circ} = \frac{a}{h} where you know the adjacent a = 11. So you can get h = \frac{a}{\cos 60^{\circ}}. Now that you have the hypoteneuse of the first triangle, you can use \tan 70^{\circ} = \frac{o}{x} where the opposite of 70 degrees is the hypoteneuse of the first triangle (whose length you've found).

    You can now use this to rearrange for x.
    Offline

    22
    ReputationRep:
    (Original post by RogerOxon)
    Calculate the hypotenuse (y) of the 60 degree triangle. That is the opposite for the 70 degree triangle.

    cos(60)=\frac{y}{11}

    \therefore y=11cos(60)

    For the second triangle, you have the opposite (y) and the adjacent (x). Using tan(70) you should be able to calculate x.
    cos 60 would be adjacent/hyp, so 11/y, surely?
    • Thread Starter
    Offline

    8
    ReputationRep:
    So is the hyp of the first triangle (the diagonal between the two triangles) 22 then? Because that's what I got originally before asking this question.
    Online

    21
    ReputationRep:
    (Original post by AnIndianGuy)
    Yes Roger got it wrong.

    You could use sin 30 too obvs
    Oops. Yes.
    • Thread Starter
    Offline

    8
    ReputationRep:
    (Original post by rogeroxon)
    oops. Yes.
    roger help me
    Offline

    22
    ReputationRep:
    (Original post by Coco_Monkey)
    So is the hyp of the first triangle (the diagonal between the two triangles) 22 then? Because that's what I got originally before asking this question.
    yes
    Online

    21
    ReputationRep:
    (Original post by Coco_Monkey)
    roger help me
    The diagonal is y:

    y=\frac{11}{cos(60)}

    Substitute for cos(60) to simplify y.

    tan(70)=\frac{y}{x}

    Rearrange and you'll get the answer.
    • Thread Starter
    Offline

    8
    ReputationRep:
    (Original post by Zacken)
    yes
    Then how does x = 7.52? Have I used the wrong ratio to find the answer? I used Tan.
    Offline

    22
    ReputationRep:
    (Original post by Coco_Monkey)
    Then how does x = 7.52? Have I used the wrong ratio to find the answer? I used Tan.
    how did you use tan
    Posted on the TSR App. Download from Apple or Google Play
 
 
 
Poll
Which accompaniment is best?
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.