Answer:

Step-by-step explanation:
r = Radius of semicircle = 
Area of semicircle is given by

The area of the semicircle is
.
Answer:
the answer is 3/4
Step-by-step explanation:
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The first one (top left) is a function. Use the vertical line test, if a vertical line crosses the line drawn on the graph twice, then it's not a function.
Answer: ∠AOB = 100°
Step-by-step explanation:
This is found in the circle geometry. The theorem in solving this stated that the angle which an arc of a circle subtends at the centre of the circle is twice that which it subtends at any point on the remaining part of the circumference of the circle
Therefore
∠AOB = 2 x ∠ACB
= 2 x 50°
= 100°