Part II Day 6

State and define the daily objective in this unit: Students will be able to solve for similar triangle problems, as well as angle-angle problems.
Define: Finding the length of any side of a triangle can b simple if you have all of the measurements of one triangle as well as all of the measurements of a similar triangle but scaled in size. Similar triangles have equal angles and equivalent side lengths. When something is "scaled in size" it basically is equivalent in size, wether it is bigger in size or smaller it will always be capable of equaling the other figure using cross multiplication. Cross multiplication is a proportion made with lengths from the same side on either triangle below another pair of lengths on the same side of either triangle. When the proportion is set-up you multiply the two numbers diagonal of each other and divide by your 3rd number to find x. This is shown below.
Example: (cross-multiplication and two similar triangles)

QUIZ
For the following similar triangles find the measure of the missing length.

1)

2)

3)

ANSWERS
1)  x/9=2/4 <--- proportion. Now solve for x
     18/4 <--- reduce to find x
     x= 4.5

2) 5/7.5 = 8/x
     7.5 x 8 = 60
    60/5 = 12
    x= 12

3) 6/4.5= x/6
    6 x 6 = 36
    36/4.5 = 8
    x= 8