Objectives:- Develop & apply formulas for the area of

triangles, parallelograms, & trapezoids.

5.2 Area of Triangles, Parallelograms, & Trapezoids

Warm-Up:The length of the rectangle is 4 inches less than 3 times the width. The perimeter is 40 inches. Find the length and the width.

Draw a right triangle, how do you think we could determine the area if we only knew the length of the legs?

Collins Writing:

3 lines 2 minutes

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Parts of a Triangle:Base: Any side of a triangleNote-for each possible choice of the base of a triangle, there is a corresponding altitude and heightAltitude: a perpendicular segment from a vertex to a line containing the base of the triangle.Height: the length of the altitude

altitude

base

The area of a triangle can be found by multiplying the base by one half of the height(altitude)

Note: the height must be PERPENDICULAR to the BASE!!!

Area =

Area = ?

35in

48in

29in21in

Area = ?

The base of one of the triangles in the pinwheel is 4 cm, the area is 14 cm2, what is the height of one triangle?

Parts of a Parallelogram:Base: Any side of a parallelogram

Altitude: a perpendicular segment from a line containing the base to a line containing the side opposite the base.

Height: the length of the altitude

altitude

base

base

𝑨𝒓𝒆𝒂=𝒃𝒉

Parts of a Trapezoid:Bases: the two parallel sides of a trapezoid

Altitude: a perpendicular segment from a line containing one base to a line containing the other base.Height: the length of the altitude

altitude

base

base

𝑨𝒓𝒆𝒂=𝟏𝟐 (𝒃𝟏+𝒃𝟐 )∗𝒉𝒐𝒓

𝒉(𝒃¿¿𝟏+𝒃𝟐)𝟐 ¿

Legs: the two non-parallel sides of a trapezoid

Example:Use the diagram and measurements given below to find the areas of the indicated figures.∆VWZ = ______

∆WXY = ______

VWXY = ______

WXYz = ______

9

8 17

10

6

W X

Z YV

HSPA questions of the day:

A C

B

2

BAC =A. 26o B. 64o

C. 77o D. 154o

m<2 =A. 26o B. 154o

C. 72o D. 103o

ABC is an isosceles triangle.AB BC and m<ABC =

Homework:Pages 308-309; Numbers 10-30