P 2 Absolute Value Distance Formula Midpoint Formula

P. 2: Absolute Value, Distance Formula, Midpoint Formula, Equations of Circles

First, recall the Cartesian Plane: (also called the rectangular coordinate system) First y Ordered pair: Quadrant y-axis x-coordinate P(3, 1) Second P(3, 1) Quadrant y-coordinate x origin Third Quadrant Fourth x-axis Quadrant

Absolute Value …tells magnitude of a number… N ot a ti on ! The absolute value of a real number a is: |a|= Ex: |5| = 5 Ex: |– 3| = 3 a, if a > 0 –a, if a < 0 0, if a = 0 Ex: | – 6| = 6 –

Distance Formula Let a and b be real numbers. The distance between a and b is: |a – b| The distance between points P(x 1 , y 1) and Q(x 2 , y 2) in the coordinate plane is: 2 d = (x 1 – x 2) + (y 1 – y 2) 2 (derived via the Pythagorean Theorem)

Midpoint Formula The midpoint of the line segment with endpoints a and b is: a + b (Number Line) 2 The midpoint of the line segment with endpoints (a, b) and (c, d) is: (Coordinate Plane) a+c 2 , b+d 2

Guided Practice Find the distance between the points: – 2, – 11 d= 9 (– 3, 1), (7, – 3) d = 2 29

Guided Practice Find the midpoint of the line segment with the given endpoints: 2. 3, – 10. 4 Midpt = – 4. 05 (5, 8), (– 6, 2) Midpt = (–½, 5)

What is a circle? ? ? The set of points in a plane at a fixed distance (radius) from a fixed point (center) y (x, y) Let’s use the distance formula to find the radius: r (h, k) x Then, what happens if we square both sides… Standard form equation for a circle

Guided Practice: Find the standard form equation of the circle. Center (– 3, 6), radius 9 Center (0, 2), radius

Guided Practice: Describe the set of real numbers that satisfy: This expression means that the distance from x to 2 must be less than 3… Thus, x must be between – 1 and 5:

Guided Practice: Prove that the triangle determined by the points (3, 0), (– 1, 2), and (5, 4) is isosceles but not equilateral. Find the lengths of all three sides using the distance formula… With only two sides congruent, the triangle is isosceles, but not equilateral!

Whiteboard Problems (formative assessment) Find the area and perimeter of the figure determined by the given points: (– 5, 3), (0, – 1), (4, 4) Prove that the triangle determined by the points D(– 3, 4), O(1, 0), and G(5, 4) is a right triangle.

Whiteboard Problems: Determine the type of quadrilateral that is defined by the points B(0, 0), A(7, 2), I(8, 12), and N(1, 10). Quad. BAIN is a parallelogram!!! Find the center and radius of the circle. Center (5, 1), radius = 11 Center (-1, 0), radius =

Homework: p. 20 -22 11 -17 odd, 23 -27 odd, 41 -51 odd Quiz P 1 -P 2 tomorrow. If you have questions over the homework you must see me before the quiz (which usually means before school 7: 158: 00). We won’t have time during class to review the HW.