- ${F_{13}} = {F_1} - {F_3} = 40 - 20 = 20N$
${F_{123}} = \sqrt {F_{13}^2 + F_2^2} = \sqrt {{{20}^2} + {{30}^2}} = 10\sqrt {13} N$
- ${F_{13}} = \sqrt {F_1^2 + F_3^2} = \sqrt {{3^2} + {3^2}} = 3\sqrt 2 N$
${F_{123}} = \sqrt {F_{13}^2 + F_2^2 + 2.{F_{13}}.Fcos(60 + 45)} = 2,69N$