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**Strangerrr****Member**- Registered: 2018-07-28
- Posts: 23

I need help checking if my answers are correct.

12. If ABC is a 30-60-90 triangle, with angle ACB at 30 degrees, and line segment AC is the diameter of the circle, then if the length of line segment AB is 4, what is the radius of the circle?

D4

A8

B2

C10

D4

E 7

F 16

13. Working with the information from 12 from here to #16, what is the measure of arc AB?

E 60 deg

A90 deg

B25 deg

C30 deg

D120 deg

E 60 deg

F 72 deg

14. What is the measure of arc BC?

D120 deg

A20 deg

B45 deg

C75 deg

D120 deg

E 15 deg

F 90 deg

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,442

hi Strangerrr

It's a property of all circumcircles that have one side as a diameter, that the angle made at the circumference is 90.

http://www.mathisfunforum.com/viewtopic.php?id=17799 post number 6.

So B = 90.

If you sketch the diagram and making BC a mirror line, reflect A and C in the mirror to get A' and C.

A'C = AC so CAA' is isosceles, and angle ACB = A'CB = 30, so ACA' = 60. This makes triangle CAA' an equilateral triangle with sides of 8.

That should help you do get the answers to these.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob Bundy

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**Strangerrr****Member**- Registered: 2018-07-28
- Posts: 23

Thank you for helping!

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,442

hi Strangerrr

It was a pleasure to help.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob Bundy

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