Day 4 ­ Angle Bisectors

1) Identify and use angle bisectors in triangles

1) Have students recall what an angle bisector is:

ANGLE BISECTOR - For ray QR to be the angle bisector of < PQS, point R must be on the interior of < PQS and < PQR must be congruent to < RQS.

Thus an angle bisector of a triangle is a segment that separates an angle of the triangle into two congruent angles. One of the endpoints of an angle bisector is a vertex of the triangle, and the other endpoint is on the side opposite that vertex.


2) Together with the students construct the angle bisector of one angle of the triangle. Have the students construct all other angle bisectors. Have them compare the relationship of medians, altitudes, perpendicular bisectors and angle bisectors.


3) Have the students link the definition of triangle angle bisector with algebra

Practice Problem: In triangle RST, segment SU is an angle bisector.

If <RSU = 2x + 15 and <UST = 5x, find the m<UST

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