48 Distance; degree-measure of an angle Ch. 3
3.8 Show that ifdis any positive real number and||is a distance function, then
d||is also a distance function.3.9 Ifαis the reflex angle with support|BACandβis the reflex angle with support
|BAF, show that if[A,F ⊂IR(|BAC)then|α|◦+|∠CAF|◦=|β|◦.3.10 Prove that ifl=ml(|BAC)andm=ml(|BAC 1 )whereA∈[C,C 1 ],thenl⊥m.3.11 Suppose thatB,C,B 1 andC 1 are points distinct fromAand thatA∈[B,B 1 ],
A∈[C,C 1 ]. Show that then ml(|B 1 AC 1 )=ml(|BAC).