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Triangles I
by Monica Yuskaitis
Copyright © 2000 by Monica Yuskaitis
Definition• Polygon – a closed many straight-
sided figure.
Copyright © 2000 by Monica Yuskaitis
Definition• Angle – two rays that meet at a
common end point.
Copyright © 2000 by Monica Yuskaitis
Definition• Degree – a unit of measurement of
an angle or arc, represented by the symbol º.
30º
Copyright © 2000 by Monica Yuskaitis
Definition• Triangle – a polygon with 3 angles
and 3 straight sides.
Copyright © 2000 by Monica Yuskaitis
Property of triangles• The sum of all the angles equals
180º degrees.
90º 30º
60º
Copyright © 2000 by Monica Yuskaitis
Property of triangles• The sum of all the angles equals
180º degrees.
90º 30º
60º
60º90º30º+
180º
Copyright © 2000 by Monica Yuskaitis
Property of triangles• The sum of all the angles equals
180º degrees.
90º 50º
40º
40º90º50º+
180º
Copyright © 2000 by Monica Yuskaitis
Property of triangles• The sum of all the angles equals
180º degrees.60º60º60º+
180º60º 60º60º
Copyright © 2000 by Monica Yuskaitis
What is the missing angle?
70º70º
?+180º70º 70º
?
Copyright © 2000 by Monica Yuskaitis
What is the missing angle?
90º30º
?+180º30º 90º
?
Copyright © 2000 by Monica Yuskaitis
What is the missing angle?
60º60º
?+180º60º 60º
?
Copyright © 2000 by Monica Yuskaitis
What is the missing angle?
30º78º
?+180º
78º 30º
?
Copyright © 2000 by Monica Yuskaitis
What is the missing angle?
40º40º
?+180º
40º 40º
?
