Triangle Area


A triangle is a 3-sided shape.
The diagram shows the same triangle with different bases and heights.
Any side of the triangle can be the base.
The height of a triangle is always perpendicular to the base.



If you remember, the area formula for parallelograms is A = bh.
The area formula for triangles is half of that, A = ½ bh.

Why is the area formula for triangles ½ of the area formula for parallelograms?

  →  		  
  →  
Take a triangle
(base and height labeled)		 Make a copy of the first triangle When you put the two triangles together,
they form a parallelogram.


Example:

area =
In the diagram, the height of the triangle is 4 cm.
The corresponding base is 6 cm.
The base is NOT 5 cm because the height is perpendicular to the side labeled 6 cm.

Now, put the values into the triangle area formula.
The answer is area = .

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