._._._._._._._._._._._._._._._._.

Răspuns:
a) MOS= 180-(75+x+45-x)=180- 120=60.
b) 45-×=90/3 => x=45-30=15.
NOR=60 (opus la varf cu MOS)
NOQ=15 (opus la varf cu MOP)
QOS=90 (SR si PQ sunt perpendiculare in O)