13. 2071 Q.No. 7a यदि \vec{p} \vec{q} \vec{r}=0, \vec{|p|}=6\vec{|q}|=\gamma \vec{|r|}=\sqrt{127} भए \vec{p}r\vec{q} विचको कोण पत्ता लगाउनुहोस्। (If \vec{p} \vec{q} \vec{r}=0,|\vec{p}|=6, \vec{|q}=7 and \vec{|r|}=\sqrt{127},find the angle between \vec{p} \vec{q} ) Ans: 60
