U6L3 Area of Triangles & Trapezoids

Do Now:•Write in planner•Get out homework to check/grade•Set up for notes•Find the circumference and area:

Area of a Triangle• The area of a triangle is half the

product of its base b and its height h.

Triangles

• A diagonal of a parallelogram divides the parallelogram into 2 congruent triangles.

• The area of each triangle is half the area of the parallelogram

• The base of the triangle can be any side.

• The height is the perpendicular distance from the base to the opposite vertex.

Practice

**Hint**: multiplying by ½ is the same

as dividing by 2

Area of trapezoids

• The area of a trapezoid is half its height multiplied by the sum of the lengths of its two bases

Trapezoids

• A parallelogram can be divided into 2 congruent trapezoids.

• The two parallel sides of a trapezoid are its bases• A = ½ (b1 + b2)h

Challenge Problem

• Find the missing measurement of each triangle.

• b = 12inh = ?A = 42

42 = ½ b(12)42 = b66 67= b

Assignment

• P. 436-437 #7-9, 13-15, 25