1. Finding Equations of Lines If you know the slope and one point on a line you can use the point-slope form of a line to find the equation. If you know the intercepts of a line, you can use the intercept form of a line to find the equation.

2. Ex. 1 Find an equation of the line with x-intercept 8 and y-intercept 4. Use the intercept form of a line.

3. Ex. 2. Find the equation of the line through (1, 4) and (5, -2) Find the slope m. Use point-slope form of a line.

4. Ex. 3. Find an equation of the line with y-intercept –3 and parallel to Put original equation in slope-intercept form A parallel line will have the same slope. Use the y-intercept given. Put in general form.

5. A segment is a median of a triangle if and only if it extends from a vertex of a triangle to the midpoint of the opposite side. Every triangle has three The point of concurrency of the medians is called the centroid.

6. A segment is an angle bisector of a triangle if and only if it bisects an angle of the triangle and has 0ne endpoint on the opposite side. Every triangle has three. The point of concurrency of the angle bisectors of a triangle is called the incenter.

7. An altitude is a segment from a vertex of a triangle perpendicular to the line containing the opposite side. Every triangle has three. The point of concurrency of the altitudes is called the orthocenter.

8. A perpendicular bisector is perpendicular to and bisects the opposite side of the triangle. The perpendicular bisectors intersect at a point that is equidistant from the vertices of the triangle. The point of concurrency of the perpendicular bisectors of the sides of a triangle is called the circumcenter.

9. Ex. 4. Write an equation of the perpendicular bisector of the segment joining A(-2, 3) and B(4, -5) Find the slope of the original segment. The slope of the perpendicular bisector would be the negative reciprocal. The perpendicular bisector intersects the segment at its midpoint. Use point-slope form of a line.

10. Another way to do example 4 would be to use the distance formula. Consider point P(x, y), if it is on the perpendicular bisector of AB, then AP = PB.