Question

Simple triangle question 100 points
What is this measure ?

Answer 1

1) they are similar by AAA postulate

2) 9.6 cm

Step-by-step explanation:

Triangles CAB and CED are similar

because:

1) both have the same angle C

(vertically opposite angles)

2) Angle A = Angle E

(alternate angles)

3) Angle B = Angle D

(alternate angles)

CA/CE = AB/ED

10/8 = 12/DE

DE = 12 × 8/10

DE = 9.6

Answer 2

see below

Angle ACE = DCE since they are vertical angles

Angle A = Angle E parallel lines cut by a transversal form congruent alternate interior angles

Angle B = Angle D parallel lines cut by a transversal form congruent alternate interior angles

When all three angles are equal, the triangles are similar.

We can use ratios to find DE

DE CE

------- = ----------

AB AC

DE 8

------- = ----------

12 10

Using cross products

10 DE = 8*12

10 DE = 96

Divide by 10

DE = 9.6