area of triangles and trapezoids
TRANSCRIPT
Area of Triangles and Trapezoids
Area of a TriangleThere are several different kinds of triangles.
bh21
A
The formula for area of a triangle is because a triangle is half of a parallelogram.
Try it!
A =
A =
A = 48 cm2
12 cm
8 cmbh
21
(12)(8)21 6
1
Try it!
A =
A =
A = 22.5cm2
9 cm
7 cm5 cmbh
21
(9)(5)21 4
5
You can see that the height is the distance between the bases. The base is the sum of the two parallel sides. So, the trapezoid is ½ of the created parallelogram.
2
1 2•So the formula is ½(b + b )h
b
b
1
2
b
You try it!Find the area of this trapezoid.
A =
A =
A = 21 in2
3 in
10 in
4 in
)hb(b21
21
10)3(421
147
1
A =
A =
A = 32 cm2
6 in8 in
2 in)hb(b
21
21
2)8(621
84
1