How do I work out the Height of this triangle if I know all sizes?

esuhl

You can only use Pythagoras' Theorum on right-angled triangles. In the examples above, sides a and b are equal, making an isosceles triangle that can be cut in half vertically, to form two identical right-angled triangles.

So... if we call the horizontal base line "b", the two equal sides "a", and the height "h":



Or in Excel, if you enter "a" in cell A1 and "b" in cell B1, you could use this formula to calculate the height:

=SQRT(A1^2-(B1/2)^2)

aliEnRIK

It fascinates me how people are coming up with all sorts of answers

I used to have to calculate things of this nature (Sometimes far more complex) then cut them on my machine. If I got it wrong I could have made 25 grands worth of scrap

[Deleted User]

Pretty sure this is covered at school when you are about 13 or 14.. it's simple ancient maths

Swan_2

aliEnRIK wrote: »

It fascinates me how people are coming up with all sorts of answers

I used to have to calculate things of this nature (Sometimes far more complex) then cut them on my machine. If I got it wrong I could have made 25 grands worth of scrap

what answer do you get RIK?

kwikbreaks

esuhl wrote: »

You can only use Pythagoras' Theorum on right-angled triangles. In the examples above, sides a and b are equal, making an isosceles triangle that can be cut in half vertically, to form two identical right-angled triangles.

So... if we call the horizontal base line "b", the two equal sides "a", and the height "h":



Or in Excel, if you enter "a" in cell A1 and "b" in cell B1, you could use this formula to calculate the height:

=SQRT(A1^2-(B1/2)^2)

When it's an isosceles right angle triangle to start with you don't need all that malarky it's just half of the hypotenuse. The first question was for a right angled triangle (within a mm at least) but the second triangle isn't one so you do need to do the calculation you and everybody else has given.

That will work for any isosceles triangle not just right angled ones because bisecting one always forms two right angled triangles.

What really intrigues me is what all these triangular bits of glass are for? A domed greenhouse?

jackieblack

kwikbreaks wrote: »

What really intrigues me is what all these triangular bits of glass are for? A domed greenhouse?

Me too, maybe a mini Eden Project type thing?

stevemcol

Kwikbreaks

It's probably me being hard of understanding but I don't see what your various posts are driving at. The initial triangle is isosceles. The technique that most people are agreed on is to bisect from the apex to base, creating two identical right angled triangles. Then simple pythag subtraction to calculate the vertical side.
I don't understand what you mean by 'the second triangle is not right angled' and 'it's just half of the hypotenuse'. Please explain.

JimmyTheWig

stevemcol wrote: »

I don't understand what you mean by 'the second triangle is not right angled' and 'it's just half of the hypotenuse'. Please explain.

In the first question, the angle at the top of the original triangle is a right angle (or looking at it a different way, both sides come down at 45 degrees).
Is this is the case then the perpendicular height required is simply half the base (which is the hypotenuse of the original triangle).

stevemcol

JimmyTheWig wrote: »

In the first question, the angle at the top of the original triangle is a right angle (or looking at it a different way, both sides come down at 45 degrees).
Is this is the case then the perpendicular height required is simply half the base (which is the hypotenuse of the original triangle).

Yes I get that but is there something in the dimensions provided that shouts 45° without doing trig. (and actually using trig I get 45.02 and 44.98°) though I suspect that's down to measuring accuracy.

JimmyTheWig

stevemcol wrote: »

Yes I get that but is there something in the dimensions provided that shouts 45° without doing trig. (and actually using trig I get 45.02 and 44.98°) though I suspect that's down to measuring accuracy.

Depends what you call trig.
a x root(2) = c
where root(2) = the square root of 2 ~= 1.4142

I don't know how the original poster who spotted it was a right-angle spotted it.
But maybe the OP would have known it was a right angle?