Question Number 149045 by mathdanisur last updated on 02/Aug/21
$$\mid\overset{\rightarrow} {\boldsymbol{{a}}}\mid\:=\:\mid\overset{\rightarrow} {\boldsymbol{{b}}}\mid\:=\:\mathrm{4}\:\:\:{and}\:\:\:{cos}\boldsymbol{\alpha}\:=\:\mathrm{60}° \\ $$$${find}\:\:\:\overset{\rightarrow} {\boldsymbol{{a}}}\:\centerdot\:\overset{\rightarrow} {\boldsymbol{{b}}}\:=\:? \\ $$
Answered by puissant last updated on 02/Aug/21
$$\overset{\rightarrow} {\mathrm{a}}.\overset{\rightarrow} {\mathrm{b}}=\mid\overset{\rightarrow} {\mathrm{a}}\mid×\mid\overset{\rightarrow} {\mathrm{b}}\mid×\mathrm{cos}\alpha \\ $$$$\alpha=\mathrm{mes}\left(\overset{\rightarrow} {\mathrm{a}};\overset{\rightarrow} {\mathrm{b}}\right) \\ $$$$\Rightarrow\:\overset{\rightarrow} {\mathrm{a}}.\overset{\rightarrow} {\mathrm{b}}=\mathrm{4}×\mathrm{4}×\mathrm{cos60}\:=\:\mathrm{8}... \\ $$
Commented by mathdanisur last updated on 02/Aug/21
$${Thank}\:{You}\:{Ser} \\ $$