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8-13.
  1. Tromika wants to calculate the area of the isosceles triangle at right. Homework Help ✎

    1. She decides to start by drawing a height from vertex A to side BC as shown below. Will the two smaller triangles be congruent? In other words, is ∆ABD ≅ ∆ACD? Why or why not?

    2. What is mDAB? BD?

    3. Determine AD. Show how you got your answer.

    4. Calculate the area of ∆ABC.

Look at the two triangles that are created. They share a side, and the ticks marks mean the sides are equal. How could they be congruent?

Yes, they are congruent by HL≅.

If the segment (height) bisects both ∠BAC and segment BC, how can you calculate the measure of half of each?

DAB = 18°
BD = 4

Which trig ratio can you use to determine this length?

How do you find the area of a triangle? Do you have enough information to calculate the area?