1-4+Angles+&+Their+Measures

You label an angle by either one point and each line or the point at the angle. Take the diagram below. The angle would be labeled as Ð ABC or Ð B. The point at the angle is always the middle point.

If two angles have the same measure than they are congruent angles. For example, if Ð A= Ð B then they are congruent.

Two angles are adjacent angles if they share a common vertex and side and have no common interior points. An interior of an angle is one point that is in-between the two rays that form the angle.

Angle addition postulate

If P is the interior of Ð ABC then Ð ABP+ Ð PBC= Ð ABC Angle classification. Angles are one of four types. Acute angles are angles below 90 degrees. Obtuse are over 90 degrees. A strait angle is 180 degrees and a right angle is 90 degrees. Acute Obtuse Right Strait Sample problems If an angle measures 140 degrees than what type of angle is it? An obtuse angle. What is the measure of Ð ABC if point P is in the interior of Ð ABC and Ð PBA=90 degrees and Ð PBC= 20 degrees? 110 degrees If Ð ABC is an obtuse angle, then what is a possible measure of Ð ABC? From above 90 degrees to below 180 degrees.

For you 1 Find Ð HIK 2 What type of angle is Ð ABC 3 If you increase Ð ABC from the previous question by 40 degrees then what type of angle is it? 4 Find Ð ABP if P is the interior of Ð ABC, Ð ABC=170 degrees and Ð PBC=5 degrees.

Helping sites [] [] http://www.mathsisfun.com/geometry/congruent-angles.html