## ErinWeeks Group Title Find mBAC in circle O. (The figure is not drawn to scale.) one year ago one year ago

1. ErinWeeks

2. ErinWeeks

A. 170 B. 95 C. 47.5 D. 42.5

3. arandomguy

do u go to connexus

4. ErinWeeks

no i go to James Madison

5. arandomguy

i was on the unit 6 test and was wondering if someone could help me with some problems

6. ErinWeeks

im on exam 6 test to

7. SmoothMath

Oh, hey. Real simple. If you can figure out the measure of the arc that the inscribed angle subtends, then the angle will simply be: $\Large \text{inscribed angle} = \frac{\text{measure of arc subtended}}{2}$

8. ErinWeeks

i dont know how to figure that out the arc -_-

9. SmoothMath

|dw:1357873734885:dw|

10. ErinWeeks

so it would be 85 .. then what do you do? can you show me

11. SmoothMath

naw gurl. it aint even.

12. ErinWeeks

im confused ...

13. SmoothMath

I can tell.

14. ErinWeeks

Helppp lol

15. ErinWeeks

would it be 90? 95? I dont know lol

16. SmoothMath

I'm sorry. The whole guessing business just kills me. Stop guessing, stop begging for answers, and show some effort.

17. ErinWeeks

i am i dont know how to do this, Im trying ..

18. SmoothMath

All of the facts you need: Two angles that form a straight line must add up to 180 degrees. An arc has the same measure as a central angle that includes it. An inscribed angle is half of the measure of the arc it includes.

19. mathmate

|dw:1357910861134:dw| @ErinWeeks We should never guess in math, or else you will always have 25% or thereabouts for your grades! :( The above diagram shows the relation between the angles subtended by the same chord AC, at the circumference B or at the centre O. If you join OB, then OA,OB,OC are all equal to the radius. Thus triangl OAB is isosceles, therefore mBAO=mABO. Similarly mBCO=mCBO. But mABO+mCBO=mAOC (exterior angles), which means finally $$mAOC=2 * mABC.$$ Hope this helps. Note: this is similar to the question I answered previously. Hope that this more detailed explanation helps you work on other problems. Please, do NOT guess your answers if you want a good grade. Understanding is faster than guessing.