1. Pick up your calculators on your way into the room. Find the numerical invariance in the table below. QT 1/8½ 416 832 100400

2. ConstantNumerical Invariant Position of point Intersection of lines Lengths of segments Measure of angles Sums of ratios What can be invariant?

3. Which measures seem invariant in triangle DEF as D moves along line CD? The area of triangle DEF The sum of the measures of angles D, E, and F

4. How do you find the area of a triangle? Area of a triangle = ½ base X height Example 1 A = ½ (7X4) A= ½(28) A= 14 units 2 Example 2 A= ½ (5X12) A = ½ (60) A = 30 units 2

5. What is the height of triangle ABC if the area is 24 in 2 and the base is 12 in ? A = ½ (bXh) 24 = ½ (12Xh) 24 = 6h 4 = h What is the base of triangle LMN if the area is 14 cm 2 and the height is 2cm? 14 = ½(bx2)

6. a.Measure of angle CDE = Measure of angle DEF b.Measure of angle CDE + EDF + EFD = 180 degrees c.Measure of angle EFD is less than measure of angle AED and Measure of angle FED is less than measure of angle BFD

7. Write your summary and turn in your Cornell Notes.