Maths: Help

[Halo_n_Horns]

if the height is 5cm and (equalateral triangle) and there is a right angle....help plz!

[junglemonkey]

Not entirely sure I understand what you mean by the question but I'll give it a shot.



If a triangle is equilateral all the sides are the same



You need the height so you split the triangle into two triangles of base 2.5 and height 5. From there you do 1/2 x base x height. So that's 1/2 x 2.5 x 5 = 6.25.



Multiply that by two to get the full triangle (you only have half) Hope thats right

[Rayne]

isn't the area of a triangle 1/2bh or half of the bas times the height.

[junglemonkey]

Crap. Weren't the sides 5cm?? I interpreted it as the sides being 5cm, sorry.

[Gostridah]

Well, if it's an equilateral triangle and the height is 5 cm...



PYTHAGORAS!



Since all the sides are the same, if you cut the triangle in half (through the height) you get two identical triangles, where h is one of the legs. So we say:



leg^2 + leg^2 = hyp^2

h^2 + 1/2 x^2 = x^2 (since x is the length of each side, and when you cut the triangle in half, one of the legs-to-be will be half the length of the hypotenuse)

25cm^2 = 1/2x^2 (note that here 25cm^2 has been already squared, but this is what you get with shitty computer notation)

50cm^2 = x^2

5 sqrt(2)cm = x



So there you have the sides, with that you should be able to get whatever you wanted.