1. 44 180 136 Angle CAB + Angle ACB + Angle ABC = 180 degrees
Turn to page S.75
Complete the triangle.
All angles must add up to _______ degrees.
Angle ABC and Angle x form a straight angle.
x is an exterior angle.
180 44
136
Angle CAB + Angle ACB + Angle ABC = 180 degrees
? = 180

2. 76 104 Angle CAB + Angle ACB + Angle ABC = 180 degrees
Turn to page S.75
Complete the triangle.
All angles must add up to _______ degrees.
Angle ACB and Angle x form a straight angle. 76
104
Angle CAB + Angle ACB + Angle ABC = 180 degrees
? = 180

3. 59 38 Angle CAB + Angle ACB + Angle ABC = 180 degrees
Turn to page S.76
Complete the triangle.
All angles must add up to _______ degrees.
Angle ABC and Angle x form a straight angle.
Angle CAB + Angle ACB + Angle ABC = 180 degrees
? = 180 38 59

4. 84 51 Turn to page S.76 Complete the triangle.
All angles must add up to _______ degrees.
Angle BAC and Angle x form a straight angle. 51 84

5. Use the lined paper after page S. 62, S. 66, or S
Use the lined paper after page S.62, S.66, or S.73 to write down these examples and solve.
Informal Argument:
I know that the sum of the interior angles of any triangle is 180 degrees.
I can find the measure of x (and prove it is true) by _________________.

6. Use the lined paper after page S. 62, S. 66, or S
Use the lined paper after page S.62, S.66, or S.73 to write down these examples and solve.
How can completing the third angle of the triangle help you to solve (or check your work for) the measure of angle x above?
How does your informal argument change in the figure above?
Informal Argument:
I know that the sum of the interior angles of any triangle is 180 degrees.
I can find the measure of x (and prove it is true) by _________________.

7. Use the lined paper after page S. 62, S. 66, or S
Use the lined paper after page S.62, S.66, or S.73 to write down these examples and solve.
Informal Argument:
I know that the sum of the interior angles of any triangle is 180 degrees.
I can find the measure of x (and prove it is true) by _________________.

8. Use the lined paper after page S. 62, S. 66, or S
Use the lined paper after page S.62, S.66, or S.73 to write down these examples and solve.
Informal Argument:
I know that the sum of the interior angles of any triangle is 180 degrees.
I can find the measure of x (and prove it is true) by _________________.

9. Use the lined paper after page S. 62, S. 66, or S
Use the lined paper after page S.62, S.66, or S.73 to write down these examples and solve.
Informal Argument:
I know that the sum of the interior angles of any triangle is 180 degrees.
I can find the measure of x (and prove it is true) by _________________.

10. Turn to page S.80

11. Turn to page S.81

12. Turn to page S.81

13. Turn to page S.81

14. Turn to page S.82

15. Turn to page S.82

16. Turn to page S.82

17. Turn to page S.83

18. Turn to page S.83