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# Sum Of The Angles Of A Triangle

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### Sum Of The Angles Of A Triangle

1. 1. Geometry Angles of a Triangle Objective: Outcome E3 – Make and apply generalizations about the sum of the angles in triangles and quadrilaterals.
2. 2. Sum of the angles of a triangle a c b
3. 3. Angles of a Triangle a c b <ul><li>Draw any triangle on a piece of paper. </li></ul><ul><li>Mark the corners a, b and c. </li></ul><ul><li>Tear the triangle into three corners. </li></ul>
4. 4. Angles of a Triangle <ul><li>Draw any triangle on a piece of paper. </li></ul><ul><li>Mark the corners a, b and c. </li></ul><ul><li>Tear the triangle into three corners. </li></ul>a c b
5. 5. Angles of a Triangle <ul><li>Arrange the three pieces so the corners are adjoining. </li></ul><ul><li>What do you notice? </li></ul>a c b
6. 6. Angles of a Triangle <ul><li>What do you notice? </li></ul><ul><li>What kind of angle to they form? </li></ul><ul><li>What is the measure of the angle? </li></ul>a c b
7. 7. Angles of a Triangle <ul><li>The sum of the angles of any triangle equals 180 °. </li></ul>a c b a + b + c = 180 °
8. 8. Finding Angles of a Triangle <ul><li>If we know two angles of a triangle, we can find the third angle by subtracting the first two from 180 °. </li></ul>80 ° 40 ° ? <ul><li>180 </li></ul><ul><li>80 </li></ul><ul><li>40 </li></ul><ul><li>? </li></ul>? =
9. 9. Finding Angles of a Triangle <ul><li>If we know two angles of a triangle, we can find the third angle by subtracting the first two from 180 °. </li></ul>80 ° 40 ° ? <ul><li>180 </li></ul><ul><li>80 </li></ul><ul><li>40 </li></ul><ul><li>60 </li></ul>? = 60 °
10. 10. Finding Angles of a Triangle <ul><li>Find the measure of the unknown angle. </li></ul>100 ° 35 ° ?
11. 11. Finding Angles of a Triangle <ul><li>Find the measure of the unknown angle. </li></ul>50° 75 ° ?