Final Review Math 1 Over Unit 3

A POLYGON is a closed figure with 3 or more straight sides.

A REGULAR polygon has all equal side lengths and angle measures.

If 2 polygons are CONGRUENT all corresponding side lengths are equal and corresponding angles are equal.

2 polygons are SIMILAR if all corresponding angles are equal and corresponding side lengths are PROPORTIONAL.

scalene- all 3 sides are different lengths

isosceles- 2 of the sides are the same length

equilateral- all of the sides are the same length

Right- 1 angle that is exactly 90°

Obtuse- 1 angle that is greater than 90°

Acute- all 3 angles are less than 90°

To find the sum of the interior angles of any polygon is found by 180(n - 2) where n = # of sides.

Example: Find the sum of the interior angles of a 18-gon.

180(16) = 2,880°

Find the total from 180(n - 2), then divide by # of sides

Example: Find EACH interior angle of a regular octagon.

180(6) = 1080°

/8 = 135°

 $\frac{x}{6}=\frac{7}{15}$  

Cross multiply 15x = 42

Then divide       $\frac{15x}{15}=\frac{42}{15}$  

x = 2.8

 $\frac{x+9}{12}=\frac{4x+7}{3}$  .

3(x+9) = 12(4x + 7)

3x + 27 = 48x + 84

27 = 45x + 84

-57 = 45x

x = -1.266666...

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