2.  Acute angles are < 90 0  Obtuse angles are > 90 0  Right angles are = 90 0  Supplementary angles total to 180 0.  Complementary angles total to 90 0.

3.  If two angles are complementary and one is 2 times greater than the other, what is the measure of the smaller angle and what type of angle is it?  X = smaller angle 2x = larger angle  Equation: x + 2x = 90  3x = 90  X = 30 and the angle is acute

4.  Vertical angles are congruent 1&4, 2&3, 5&8, 6&7  Alternate interior angles are congruent 3&6, 4&5  Alternate exterior angles are congruent 1&8, 2&7  Corresponding angles are congruent 1&5, 3&7, 2&6, 4&8  Same side interior angles are supplementary 3&5, 4&6 1 2 3 4 5 6 7 8

5. 1 2 4 3 5 6 8 7 If <1 = 2x+3 and <5=x+7 What is the value of x? 2x-3 = x+7 X= 10

6.  The sum of the angles of a triangle is 180°.  Isosceles triangle – 2 sides and base angles congruent  Equilateral triangle – all sides and angles congruent  The sum of the two remote interior angles = the value of the exterior angle

7.  In a triangle the second angle is 2 time the first angle. The third angle is 5 more than the second angle. Find the measure of each angle. x 2x 2x+5 X + 2x + (2x +5) = 180 5x + 5 = 180 7x =

8.  Only works with a RIGHT triangle  SIDE 2 + SIDE 2 = HYPOTENUSE 2  a 2 + b 2 = c 2  But Implies:  if a 2 + b 2 < c 2 C is an acute angle (<90 °)  if a 2 + b 2 > c 2 C is an obtuse angle (>90 °)

9.  Parallelogram – ◦ opposite sides are parallel and congruent ◦ Opposite angles are = ◦ The diagonals bisect each other  Rectangle – a parallelogram with right angles  Square – a rectangle with all sides equal  Trapezoid: has one pair of parallel sides  The Sum of the angles of a polygon = 180(n-2)

10. What is the sum of the angles of a hexagon: 180(6-2)==720

11. Side-Side-SideAngle-Side-Angle 12

12. Side-Angle-Side  When trying to prove that two triangles are congruent, use matching parts and figure out which congruence postulate to use!

13.  If triangles are similar, the sides are in proportion and so are the perimeters 12 4 x 2 6 9

14.  r= radius d= Diameter  2r=d  Circumference: C = 2Πr  Area = A = Πr 2  Circles contain 360°

15. 1. Find the area of a circle with diameter = 12 “  A. 144Π  B. 36 Π  C. 12 Π  D. 6 Π The correct answer is B

16.  Central Angle – angle formed by two rays extending from the center

17.  Find the length of the arc intercepted by a 30 degree angle in a circle with radius = 4. arc = (30 x 8Π) / 360 arc =

18.  Inscribed angles have their vertex on the circle and the intercepted are = ½ the measure of the angle

19.  Inscribed – inside an object ◦ The circle is inscribed by the square  It just touches the edges  Circumscribed – surrounding an object ◦ The circle circumscribed the square  It just touches the edges