Answer:
9. m∠1 = 140°
10. m∠2 = 40°
11. m∠3 = 65°
12. m∠4 = 75°
Explanation:
[9] To find this measurement angle, we can use the Exterior Angle Theorem. This states that an exterior angle of a triangle will be equal to the two opposite angles added together.
60° + 80° = m∠1
140° = m∠1
[10] For this angle, we can use the knowledge of straight angles. A straight angle is equal to 180 degrees.
m∠1 + m∠2 = 180°
140° + m∠2 = 180°
m∠2 = 40°
[11] We will find the other two angles in the triangle to find this angle. There are 180 degrees within a triangle and a straight line is equal to 180 degrees.
The blank angle is 180° minus 105°, which is 75°.
Then, m∠3 = 180° - 75° - m∠2 = 180° - 75° - 40° = 65°.
[12] Again, we can use the measurement of a straight line (or straight angle) to find m∠4.
m∠4 = 180° - 105° = 75°