LESSON 8: USING FORMULAS IN GEOMETRY

Geometry

FORMULAS

• Formula: a mathematical relationship expressed with symbols

• Perimeter: the sum of the side lengths of a closed geometric figure

• Often thought of as the distance around a figure

• Area: the size of the region bounded by the figure

• Pythagorean Theorem: , where and are the legs of a right triangle and is the hypotenuse

EXAMPLE

Find the perimeter of the triangle.

8 in.

8 in.8 in.

YOUR TURN

Find the perimeter of the rectangle:

145 cm

123 cm

EXAMPLE

Find the length of the rectangle.

𝐴=108 𝑖𝑛2

𝑙

9 in.

YOUR TURN

Find the base of a rectangle with an area of and a length of 6 cm.

EXAMPLE

Find the area of the triangle.

3 ft5 ft

YOUR TURN

Find the area of a triangle with a hypotenuse of 17 millimeters and a side length of 15 millimeters.

EXAMPLE

Much of the world uses degrees Celsius, but a few countries use degrees Fahrenheit. For scientists and travelers, converting between Celsius and Fahrenheit is an important skill. The formula is .

If it is , what is the temperature in degrees Fahrenheit?

YOUR TURN

If it is , what is the temperature in degrees Fahrenheit?

HOMEWORK QUESTIONS

CORRECTING HOMEWORK

• Get your homework out so I can stamp it.

• If you do not have your homework complete, write your name on the board.

• Use red pen/pencil to correct.

• Trade with someone who has the homework done.

• If you didn’t get it done, you need to be working on finishing it now. Remember no cheating and no work = no credit.

• Make sure you write CB with your name or you will lose your citizenship points for today.

HOMEWORK

• 1st and 2nd hour: Lesson 8: b, c, e-I, 3-8, 13-25, 27-30

• 3rd hour: Lesson 8: b, c, e-I, 6, 7, 14, 15, 16, 19, 22, 29