1. Geometry OTQ
Name each part of the right triangle and isosceles triangle.
leg
hypotenuse
_________
leg
_________
_________
leg
_________
base
_________
leg
_________

2. Homework Questions?

3. What standard will I learn?
What will I be able to do?
Apply the Triangle Angle-Sum Theorem and
Exterior Angle Theorem
What standard will I learn?
12.0 Students find/use measures of sides/angles
of triangles

4. 4.2 Triangles and Angles

5. HEY….THERE IS SOME WEIRD ABOUT THE ANGLES OF A TRIANGLE2 1 3
m<1 + m<2 + m<3 = 180°

6. m<A + m<B + m<C = 180°
Triangle Sum Theorem
The sum of the measures of the interior s of a ∆ is 180o. A B C
m<A + m<B + m<C = 180°

7. Ex 1
Solve for x.
x = 180
126 + x = 180
x = 54 36 x

8. Example 2:
One of the acute angles in a right triangle measures 4x° and the other is 6x°. Find the value of x? 4x 6x
4x + 6x + 90= 180
10x + 90 = 180
10x=90
x=9

9. Interior VS Exterior
An interior angle is formed by two sides of a triangle. An exterior angle is formed by one side of the triangle and extension of an adjacent side.
4 is an exterior angle.
Exterior
Interior
<1, <2, and 3 are interior angle.

10. Exterior Angle Theorem
The measure of an exterior  of a ∆ is equal to the sum of the measures of the 2 non-adjacent interior s. A
m1 = mA + mB 1 B C

11. Example 3: Ext.  Thrm. Find mB. mA + mB = mBCD
15 + 2x + 3 = 5x – 60
2x + 18 = 5x – 60
78 = 3x
mB = 2x + 3
= 2(26) + 3
= 55°
26 = x

12. Homework is on the next slide
CLASSWORK
Pages 250 – 253 #’s 10, 12, 22, 24, 26, 28, 30, 36, 46
Homework is on the next slide

13. Do your HOMEWORK or zombies will be sent to your HOUSE!!!
Page 254 #’s 56, 60, 64, 66
Do your HOMEWORK or zombies will be sent to your HOUSE!!!