## ErinWeeks 2 years ago Find mBAC in circle O. (The figure is not drawn to scale.)

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.