Question

Given: DR tangent to Circle O.

Answer 1

Answer:

I believe the answer is 110.

Answer 2

Answer:

110°

Step-by-step explanation:

In this problem we need to use the Inscribed Angle theorem, which states that an inscribed angle is one-half its subtended arc.

$\angle C=\frac{1}{2}arc(DB)=70\°$

Then, we use the theorem about a cyclic quadrilateral, which is an inscribed quadrilateral: "the opposite angles in a cyclic quadrilateral are supplementary".

$\angle C + \angle A = 180\°\\\angle A = 180\° - \angle C\\\angle A = 180\° - 70\° \\\angle A = 110\°$

Therefore, the answer is 110°