+0  
 
0
181
1
avatar+78 

Points $A,$ $B,$ and $C$ are placed on a circle centered at $O$ as in the following diagram:

 

 

If AC = BC and angle OAC = 18 degrees then how many degrees are in angle AOB?

 Jun 29, 2018
 #1
avatar+98196 
+1

Draw  radius OC

 

And since  OC = OA, then angles OCA  and OAC  are equal 

 

Then angle  COA  =  180   - 18  -18 = 180  - 36  = 144°

 

And by symmetry, angle BOC = 144°

 

So angle AOB  = 360  - 144 - 144  = 360 - 288  = 72°

 

 

cool cool cool

 Jun 29, 2018

36 Online Users

avatar
avatar
avatar
avatar
avatar
avatar