Find ABplease help :-)
1 answer:
Answer:
Therefore,
l(AB) = 15 units
Step-by-step explanation:
Given:
AD = DC
angle DBA = angle DBC = 90°
AB = 5x
CB = 4x - 3
To Find:
AB = ?
Solution:
In Δ ABD and Δ CBD
AD ≅ DC ……….{Given}
∠ DBA ≅ ∠ DBC …………..{measure of each angle is 90° given}
DB ≅ DB ....……….{ Reflexive property}
Δ ABD ≅ Δ CBD ..........….{By Hypotenuse Leg Theorem}
∴ AB ≅ CB ..............{corresponding sides of congruent triangles}
on substituting the values we get
Now we require AB
Therefore,
l(AB) = 15 units
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<h3>Proof:</h3>
Refer to the attached figure.
There are a couple of ways you can go at this. One is to show the sums of the marked angles are the same, hence ∠B ≅ ∠D. Instead, we're going to show that ΔABD ≅ ΔCDB, hence ∠A ≅ ∠C.
1. AB║DC and BC║AD . . . . given
2. BD is a transversal to both AB║DC and BC║AD . . . . given
3. ∠CBD ≅ ∠ADB . . . . alternate interior angles where a transversal crosses parallel lines are congruent
4. ∠CDB ≅ ∠ABD . . . . alternate interior angles where a transversal crosses parallel lines are congruent
5. BD ≅ BD . . . . reflexive property of congruence
6. ΔABD ≅ ΔCDB . . . . ASA postulate
7. ∠A ≅ ∠C . . . . CPCTC
∠A and ∠C are opposite angles of parallelogram ABCD, so we have shown what you want to have shown.