Which formula would be used to find the measure of angle 1?
1/2(a° + b°). 
1/2(a° –  c°). 
1/2(b° + c°). 
1/2(a° – b°). 
-Answer-
D. 1/2(a° – b°).
                                             
                                          
                                          
                                        
											 
			                   
					                  