1. The area of a parallelogram and a triangle
Polygon Areas 2
The area of a parallelogram and a triangle
Tandi Clausen-May
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2. Click the mouse only when you see or
If you click too soon you will miss the best bits.
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Click to see
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3. The area
of a parallelogram
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4. We know that Area of a rectangle = length of a row × number of rows
height
base
Area of a rectangle
= length of a row × number of rows
= base × height
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5. We can shear the rectangle into a parallelogram.
height
base
parallelogram Area of the rectangle
Area of the rectangle
Click to see the rectangle shear
= base × height
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6. Click to see the rectangle shear
A triangle is half of a rectangle.
We can shear the rectangle into a parallelogram.
We have sheared the triangle too!
Click to see the rectangle shear
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7. Click to see the triangle shear
Let’s shear some more triangles.
Click to see the triangle shear
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8. Click to see these triangles shear
The triangles are all different shapes, but they all have the same area.
Click to see these triangles shear
They have the same area as this one.
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9. They are all half the base times the height
base × height 2
Area =
height
base
They are all half the base times the height
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10. Click to see the triangle shear
Summary
Area = base × height 2
Click to see the triangle shear
height
base
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11. The End
Tandi Clausen-May