30 cm
1 answer:
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Answer:
1. ∠ABD = 20°.
2. Arc AB = 140°.
3. Arc AD = 40°.
Step-by-step explanation:
Given information: ∠ADB = 70°. BD is diameter.
According to Central angle theorem, the central angle from two chosen points A and B on the circle is always twice the inscribed angle from those two points.
By Central angle theorem,
Using angle sum of property in triangle ADB we get,
.
Draw a line segment AO.
In triangle AOD, AO=OD, so
Using angle sum property in triangle AOD,
Therefore length of arc AD is 40°.
The angle AOD and AOB are supplementary angles.
Therefore length of arc AB is 140°.
