## Elementary Geometry for College Students (7th Edition) Clone

$m\widehat {ACB}=270^{\circ}$
The measure of the whole arc of a circle equals $360^{\circ}$. Subtract out the known arc... $360-m\widehat {BC}=m\widehat {ACB}$ $360-90=270$ $m\widehat {ACB}=270^{\circ}$