4.1 Triangle Angle Sum and Properties. How many degrees in a triangle? The sum of the angles in any triangle is exactly 180 degrees.

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Presentation transcript:

4.1 Triangle Angle Sum and Properties

How many degrees in a triangle? The sum of the angles in any triangle is exactly 180 degrees

Classify Triangles by Angles Right - having one angle of 90 degrees Obtuse – having one angle over 90 degrees Acute – having all its angles under 90 degrees

Classify triangles by side Equilateral – all the sides are the same length Isosceles – Two sides are the same length Scalene – No sides are the same length

Interior and Exterior angles Interior angles are in red Exterior angles are in yellow

Exterior angle Theorem How much is X ? Notice that the value of X is the same as the sum of the 50 and 60 degree angles!

Exterior Angle Theorem An exterior angle of a triangle is always equal to the sum of the interior angles that are not adjacent to it.

Find X

Acute Angles of a Right Triangles The acute angles of a right triangle are always complementary