*Proof:* As the measure of an inscribed angle is equal to half the measure of its intercepted arc, the inscribed angle is half the measure of its intercepted arc, that is a straight line. As the arc"s measure is $180^\circ$, the inscribed angle"s measure is $180^\circ\cdot\frac{1}{2} = 90^\circ$.$\blacksquare$

When I checked the solution on the internet there were a whole bunch of other more complicated proofs. Is mine valid? If it is invalid, could someone tell me why?

Thank you,

Paul

geometry circles proof-verification

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edited Oct 29 "13 at 13:26

amWhy

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asked Oct 29 "13 at 12:55

Paul FilchPaul Filch

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## 1 Answer 1

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$\begingroup$

**Hint**

Draw the radius from the center of the circle to the point that you think it has an angle of $90$ degrees and write down the angles:

$2(x+y)=180$

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answered Oct 29 "13 at 14:44

newzadnewzad

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