Any maths wizards on here please? Updated

claire21

If I have a square based pyramid but the only fact I know is the length of the base sides (I don't have volume or slant measurements) how do I work out the height?

**professor~yaffle**

can you work it out by pythagorus?

one side would be the length of the side of the base

the other side would be half that, presumably, if the pointy bit of the pyramid is in the centre of the square

so then you'd just need to find the third side, which would be the height?

tillyenna

I don't think you can.


Suppose you have a 1x1 square, and then a triangular pyramid on top of it with sharp angles (close to right angles) it's going to be much taller than if you had the same square, with much flatter angles.

cherryblossomzel

I don't think you can. Using the same base size, you can have a pyramid that is more or less pointy, thereby altering the height. You need something else.

Unless they're assuming some kind of standard angle measurement or something?

claire21

Sons gone out now, I will get the exact question when he's back in, but I just couldn't understand it, I thought you couldn't know unless you had one more know measurement.

Please come back later and she if you can help me.

**professor~yaffle**

I'm picturing something like this:



maybe you need the length of the side of the pyramid as well as the base.. hmm...

NY1986

Sounds like it will be trigonometry you'll need (SOH CAH TOA) - it may help if you find out what topic he's doing and at what level.

claire21

I thought maybe you just altered the formula that you use for working out the volume but didn't know how to do that, but as you all now think it doesn't appear to be that. There must be more in the question that gives you something else to go on. It was on mymaths revision so I can't log in until he gets back.

It was revision for higher level maths mock gcse.

Caroline_a

Who is doing the exam, you or him? If it's him I'm not sure you should be working on it while he's gone out!

claire21

He is of course but he spent 20 mins on Google tying to find answer and going through his notes and couldn't get anywhere. I thought if I could just find the formula he could then work it out.

El_Capitan

**professor~yaffle** wrote: »

I'm picturing something like this:



maybe you need the length of the side of the pyramid as well as the base.. hmm...

I think you need SOH CAH TOA. I don't know if this is right but is it...

(Assuming the point is above the centre of the square)

First of all, find the length of the base of the triangle with side h (the one that finishes in the centre of the square) by using the known length of the side of the square base and the angle of 45 degrees (as that is a bisected right angle). We'll call this y.

Once this is found, find h using the 90 degree angle formed between the side h from the centre of the square and y.

Let me know if anyone thinks I'm right!