Which equation is correct regarding the measure of angle 1 ?
A
m angle 1 is equal to 1 half times open paren A plus c close parenB
m angle 1 is equal to 1 half times open paren b minus d close parenC
m angle 1 is equal to 1 half times open paren b plus d close parenD
m angle 1 is equal to 1 half times open paren A minus c close paren