Area and Surface Area Day 9

Formula for the Area of a Triangle

Day 9

Objective:

Today I will compare, contrast, and critique different strategies for determining the area of a triangle so that I can use the area formula to find the area of a triangle. I know I am successful when I complete Cool Down 9 to earn a 4.

Bases and Heights of a Triangle

Study the examples and non-examples of bases and heights in a triangle. Answer the questions that follow.

These dashed segments represent heights of the triangle.

These dashed segments do not represent heights of the triangle

Multiple Select

Select all the statements that are true about bases and heights in a triangle.

• Any side of a triangle can be a base.

• There is only one possible height.

• A height is always one of the sides of a triangle.

• A height that corresponds to a base must be drawn at an acute angle to the base.

Multiple Select

Select all the statements that are true about bases and heights in a triangle.

• A height that corresponds to a base must be drawn at a right angle to the base.

• Once we choose a base, there is only one segment that represents the corresponding height.

• A segment representing a height must go through a vertex.

Open Ended

Finding the Formula for Area of a Triangle

Complete in the book!

Applying the Formula for Area of Triangles

For each triangle, identify a base  measurement that you can use to find the area of the triangle. Then, find the area of any three triangles. Show your reasoning.

Open Ended

Find the area.

Open Ended

Find the area.

Open Ended

Find the area.

Open Ended

Find the area.

Open Ended

Find the area.

Multiple Choice

How do you find the AREA of a TRIANGLE?

• Length x Width
• Base x Height divided by 2
• 1/3 (Length x width)
• Base x Height