Question

PLEASE HELP !!! Find the measure of y A. 43 B. 90 C. 53 D. 47

Answer 1

Answer: A. 43

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Explanation:

Notice how inscribed angles x and y subtend (or cut off) the same minor arc measure. This means that x = y. So if we find x, we found y also.

The vertical line is a diameter of the circle. The blue angle marked in the diagram below is a right angle due to Thales Theorem, which is a special case of the inscribed angle theorem. Thales Theorem says that any inscribed angle in a semicircle is 90 degrees.

Therefore the triangle marked in red (same diagram) is a right triangle, allowing us to say

x+47+90 = 180

x+137 = 180

x = 180-137

x = 43

So y = 43 as well.