What is the length of DE? B
15
49"
A
18
C D
12
A. 6
B. 15
O C. 10
D. 9

Step-by-step explanation:

Yes

Theorem 8.3: If two angles are complementary to the same angle, then these two angles are congruent.

∠A and ∠B are complementary, and ∠C and ∠B are complementary.

Given: ∠A and ∠B are complementary, and ∠C and ∠B are complementary.

Prove: ∠A ~= ∠C.

 StatementsReasons

1.∠A and ∠B are complementary, and ∠C and ∠B are complementary.Given

2.m∠A + m∠B = 90º , m∠C + m∠B = 90ºDefinition of complementary

3.m∠A = 90 º - m∠B, m∠C = 90º - m∠BSubtraction property of equality

4.m∠A = m∠CSubstitution (step 3)

5.∠A ~= ∠CDefinition of ~=

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step-by-step explanation: