Giving brainliest to anyone who answers 
in the diagram below A,B,C and D are points on a circle having center O.
PBT is a tangent to the circle at B
Reflex BOC=O1 =310 as shown in the diagram below 
Calculate giving reasons the value of 
D1
B3
B1 if it is given that A=60
                                             
                                          
                                          
                                        
											 
			                  