Maria G.

asked • 08/15/15

one angle of a triangle measures 120 degrees. the other two angles are congruent. write and solve an equation to find the measure of the congruent angels.

Please help me on this problem thank you

1 Expert Answer

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Arthur D. answered • 08/15/15

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the measures of the 3 angles of a triangle add up to 180 degrees
x=the unknown angle
the 2 unknown angles are congruent
120+x+x=180
120+2x=180
2x=180-120
2x=60
x=30 degrees for each of the congruent angles
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Diana D.

Can you explain the steps/procedures?
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08/17/16

Arthur D.

tutor
The measures of the 3 angles of a triangle added together always equals 180 degrees. One angle has a measure of 120 degrees and the other 2 angles are equal in measure (that's what congruent means). Therefore 120 + some unknown angle + the third unknown angle equals 180 degrees. The 2 unknown angles have the same measure.
180-120=60 degrees for the 2 unknown angles added together. The unknown angles are again equal in measure.
60/2=30 degrees is the measure for each unknown angle.
Algebraically, let some variable, say x, equal the unknown angles. The equation becomes 120+x+x=180
120+x+x=180
120+2x=180
2x=180-120
2x=60
x=60/2
x=30 degrees for each unknown angle.
check: 120+30+30=180
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08/17/16

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