Chapter 7 Day 4
I.
Go over HW pg. 162 #2 – 20 evens
II.
Triangles
III.
HW Pg. 167 – 168 #1 – 5, 7 – 11, 14 – 16, 18, 20
Algebra I
Ch 7 Notes Day 4
Triangles
Name ________________________
Date ________________ Period ___
Triangles

_______________ - A closed figured formed by 3 line segments
Ex.)

_______________ - A line segment with one endpoint at any vertex extending to the line containing the
opposite side and perpendicular (  ) to that side.
Ex.)

_______________ - A line segment with one endpoint at any vertex of a triangle extending to the
midpoint of the opposite side.
Ex.)

_______________ - A line segment with one endpoint at any vertex of the triangle, extending to the
opposite side so that it evenly divides the vertex angle.
Ex.)
Important Information About Triangles
1. The sum of the measure of the angles of a triangle is _________
2. The longest side is opposite the _______________
Ex.)
3. The smallest angle is opposite the _______________
Ex.)
4. An exterior angle of a triangle = sum of the measure of 2 remote (nonadjacent) interior angles
Ex.)
5. The sum of any 2 sides of a triangle is greater than the third side Triangle Sides Clip
Ex.)
Classification of Triangles by Sides
Name
Description
No 2 sides are equal
No 2 angles are equal
Two sides, called the legs, are
equal. The third side is the base.
Two angles, called the base angles
are equal. The third angle, called
the vertex angle, is opposite the
base. Two sides of a triangle are
equal if and only if the angles
opposite these sides are equal. An
altitude drawn from the vertex
angle bisects the angle and the base
All three sides are equal. These
triangles are also equiangular; all
angles are equal and each angle =
60°
Example
Classification of Triangles by Angles
Name
Description
All angles are acute. That is, each
angle is less than 90°
One angle is obtuse. That is, one
angle is between 90° and 180°
One angle is a right ( 90°) angle.
The side opposite the right angle is
the hypotenuse. The other two
sides are the legs. The Pythagorean
Theorem is true of all right
triangles: a2 + b2 = c2
Pythagorean Theorem
 In a right triangle, the square of the hypotenuse = sum of the squares of the legs
Ex.)
Note: Pythagorean Triplets (and multiples)
Example
Examples:
1. In  ABC m  A = 52, m  B = 16
a. Classify  ABC as acute, right or obtuse
b. Classify  ABC as scalene, isosceles or equilateral
2. Determine whether the given sides could be a  . Is it is right  ?
a. 5, 6, 8
b. 30, 24, 18