Sums of Angles of a Triangle including Length of Sides & Measures of Angles

T.i.P.S.

Students will need to practice with hands-on materials and pictures first in order to understand the three additional properties of triangles. In order to master this standard, students should be able to demonstrate this knowledge by solving problems and providing examples and non-examples. One of the best items to show these properties are chenille stems (pipe cleaners) because they can be bent and are flexible. Strips of paper with brads attaching them will work as well for flexibility.

Example

Patricia drew a triangle as shown below.

Each of the following could be measures for Angle A or B except
     a) 63˚ because Angles A and B are obtuse and are larger than 90˚.
     b) 25˚ because Angles A and B are equivalent and 25 + 25 does not equal 90˚.
     c) 90˚ because it is impossible since the sum of all three angles must equal 180˚.
     d) 45˚ because Angles A and B are not equivalent.

Hint
Possible Solution

TEKS

Supporting Standard

6.8 Expressions, equations, and relationships. The student applies mathematical process standards to use geometry to represent relationships and solve problems. The student is expected to:

(A) extend previous knowledge of triangles and their properties to include the sum of angles of a triangle, the relationship between the lengths of sides and measures of angles in a triangle, and determining when three lengths form a triangle

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