A circle is a curve sketched out by a point moving in a plane. The measure of a is 70°. The correct option is B.
What is a circle?
A circle is a curve sketched out by a point moving in a plane so that its distance from a given point is constant; alternatively, it is the shape formed by all points in a plane that are at a set distance from a given point, the centre.
In the given circle, the line AC is the diameter of the circle, therefore, the measure of ∠ABC will be 90°.
∠ABC = 90°
This is because a triangle formed on the diameter of the circle such that all the vertices of the triangle intersect the circle, then the angle opposite to the diameter is a right angle.
Now, in ΔABC, the sum of all the angles of the triangle can be written as,
∠ABC + ∠BCA + ∠BAC = 180°
90° + a + 20° = 180°
110° + a = 180°
a = 180° - 110°
a = 70°
Hence, the measure of a is 70°.
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