b
\(\mathop A\limits^ \to  \) અને \(\mathop B\limits^ \to  \) વચ્ચેનો ખૂણો \( =110^0 - 20^0 = 90^0 \) 

\(R\,\, = \,\,\sqrt {{A^2}\,\, + \;\,{B^2}\,\, + \;\,2AB\,\cos \,\,90^\circ } \,\, = \,\,\sqrt {{5^2}\,\, + \;\,{{12}^2}} \,\, = \,\,13m\)

સદીશ \(\mathop A\limits^ \to  \) માથી \(\mathop R\limits^ \to  \) નો ખૂણો \(\alpha \) છે તેમ લો.

\(\tan \,\,\alpha \,\, = \,\,\frac{{B\,\,\sin \,\,\theta }}{{A\,\, + \;\,B\,\,\cos \,\,\theta }}\,\, = \,\,\frac{{12\,\,\sin \,\,90^\circ }}{{5\,\, + \;\,12\,\,\cos \,\,90^\circ }}\,\, = \,\,\frac{{12\,\, \times \,\,1}}{{5\,\, + \;\,12\,\, \times \,\,0}}\,\, = \,\,\frac{{12}}{5}\)

અથવા \(\alpha \,\, = \,\,{\text{ta}}{{\text{n}}^{{\text{ - 1}}}}\,\,\left( {\frac{{12}}{5}} \right)\,\) સદીશ \(\mathop A\limits^ \to  \) અથવા \(\left( {\alpha \,\, + \;\,20^\circ } \right)\,X\,\) અક્ષ સાથે