Everything you ever wanted to know about Triangles

Triangles ae very important shapes. Not only are they the basic 2-dimentional shape, from which all other rectilinear shapes (shapes with straight sides) are built up, but they make very strong, rigid shapes, which are used in many structures.

As you can see in the diagram above the area of the right angled triangle is half of the area of the rectangle. This gives us the formula A=½bh that is, Area = ½ of the base times the height					The same formula works for any triangle, because cutting the yellow triangle from the blue rectangle leaves two blue triangles which will fit on top of the yellow triangle. So again, the triangle has half the area of the rectangle.
The internal angles of a triangle always add up to 180º The external angles always add up to 360º					There are other formulae for the areas of triangles Pythagoras Theorem for the lengths of right-angled triangles. Trigonometry - Right-angled triangles - All triangles

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