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

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

Reply 1

sweet boner

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?

Reply 2

Coco_Monkey

OP

8

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.

Reply 3

sweet boner

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

Reply 4

Coco_Monkey

OP

8

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

Reply 5

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?

Reply 6

sweet boner

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.

Reply 7

Coco_Monkey

OP

8

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

Reply 8

Vexillarius

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.

Reply 9

Coco_Monkey

OP

8

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.

Reply 10

RogerOxon

21

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.

(edited 6 years ago)

Reply 11

Zacken

22

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

.

Reply 12

Zacken

22

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?

Reply 13

Coco_Monkey

OP

8

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.

Reply 14

RogerOxon

21

Original post by AnIndianGuy

Yes Roger got it wrong.

You could use sin 30 too obvs

Oops. Yes.

Reply 15

Coco_Monkey

OP

8

Original post by rogeroxon

oops. Yes.

roger help me

Reply 16

Zacken

22

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.