Transcript Areas of Parallelograms, Triangles, and Rhombuses

Areas of Parallelograms,
Triangles, and Rhombuses
Lesson 11.2
Geometry Honors
Objectives: Know and use the
formulas for the areas of
Parallelograms, Triangles, and
Rhombuses
Lesson Focus
The purpose of this lesson is to state and prove the formulas
for the areas of parallelograms, triangles, and rhombuses.
Only the key steps of each proof are shown.
Area of Parallelograms
Theorem
The area of a parallelogram equals the product of a base
and the height to that base.
A = bh
Area of Triangles
Theorem
The area of a triangle equals half the product of the base
and the height to that base.
A = ½ (bh)
Area of Rhombuses
Theorem
The area of a rhombus equals half the product of its
diagonals.
A = ½(d1d2)
Areas of Parallelograms, Triangles,
and Rhombuses
Example 1: Find the area of a triangle with base 6.3cm and
corresponding height 9.8cm.
Example 2: Find the area of a parallelogram with base 4 3
and corresponding height 3 5 .
Example 3: Find the are of a rhombus with diagonals 6 and 8.
Example 4: Find the area of an isosceles triangle with sides 12,
12, 10.
Written Exercises
Problem Set 11.2, p.431: # 2 - 20 (even);
Handout 11-2