Area of a Triangle

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# Area of a Triangle - PowerPoint PPT Presentation

Area of a Triangle . What is a triangle?. All t riangles are related to rectangles or parallelograms :. You can draw a diagonal line in any rectangle or parallelogram. Each rectangle or parallelogram is made up of two triangles!. What is the Area of a Triangle?.

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### Area of a Triangle

What is a triangle?

All trianglesare related to rectangles or parallelograms:

You can draw a diagonal line in any rectangle or parallelogram.

Eachrectangle or parallelogram is made up of two triangles!

What is theAreaof a Triangle?
• Theareaformula for a rectangle or a parallelogram is: A = bh.
• Each triangle is ½of a rectangle or a parallelogram.
• There are twotriangles in these shapes!
The Formula!
• Remember the area formula for a rectangle or parallelogram is A=bh and that each rectangle and parallelogram has TWOtriangles in their shape.
• Using this information to develop your own formula.
Can I have a drum roll please?!

Without further ado your formula should look something like…

• Theareaformula for a triangleis
• It can also be written as
Finding the Area of a Triangle

Determine which measurement is theheight:

Theheightis outside the triangle

The height is inside the triangle

The height is a sideof the triangle

Finding the Area of a Triangle
• Pay close attention to the pictures below. You may notice that some of the triangles have been rotatedorhidden in pictures.
• Findbaseandheightin these examples:

base = 10 cm

height = 9 cm

base = 12.1 m

height = 6.4 m

base = 7 yd

height = 4 yd

Applying the Area Formula
• Write the area formula exactly as it appears on the FCAT Reference Sheet.
• Rewrite the area formula substituting the values that you know.
• Solve one step at a time rewriting after each step.
Applying the Area Formula

Example: Find the area of the triangle shown below.

A = ½ bh

A = ½ × 15.6 × 11.25

A = ½ × 175.5

A = 87.75 square meters

Rally Coach
• Students sit in pairs.
• First Problem: Partner A solves; Partner B coaches and praises.
• Next Problem: Partner B solves; Partner A coaches and praises.
• Continue solving problems.
Finding the Area of a Triangle

With your shoulder partner find the area of the following triangles using Rally Coach.

1.

2.

3.

4.

Finding the Area of a Triangle

With your shoulder partner find the area of the following triangles using Rally Coach.

1.

90 cm2

2.

425.25 mm2

3.

45 cm2

4.

Find the area of the following two triangles independently.

5 cm.

6 ft.

7 cm.

3 ft.

8 km.

4 mm.

9 mm.

11 km.

Find the area of the following two triangles independently.

18 mm2

44 km2

• 9 ft2
• 17.5 cm2
Finding the Area of a Triangle

From where and how did we derive the area of a triangle formula?

Exit Question

Independently find the area of the following triangle on a separate slip of paper. This will act as your exit ticket.