Question Number 114514 by mohammad17 last updated on 19/Sep/20
Commented by bobhans last updated on 19/Sep/20
$$\left({B}\right)\:\overset{\rightarrow} {{u}}.\overset{\rightarrow} {{v}}\:=\:\mid\overset{\rightarrow} {{u}}\mid.\mid\overset{\rightarrow} {{v}}\mid\:\Leftrightarrow\:\mathrm{cos}\:\alpha=\mathrm{1} \\ $$$$\:\alpha=\mathrm{0}° \\ $$
Commented by mohammad17 last updated on 19/Sep/20
$${wow}\:!\:{thank}\:{you}\:{sir} \\ $$
Answered by bobhans last updated on 19/Sep/20
$$\left({A}\right)\:\overset{\rightarrow} {{a}}.\overset{\rightarrow} {{b}}\:=\:\mid\overset{\rightarrow} {{a}}×\overset{\rightarrow} {{b}}\mid\: \\ $$$$\mid\overset{\rightarrow} {{a}}\mid.\mid\overset{\rightarrow} {{b}}\mid.\mathrm{cos}\:\alpha=\mid\overset{\rightarrow} {{a}}\mid.\mid\overset{\rightarrow} {{b}}\mid.\mathrm{sin}\:\alpha \\ $$$$\rightarrow\:\mathrm{tan}\:\alpha=\mathrm{1}\:;\:{a}=\frac{\pi}{\mathrm{4}},\:\frac{\mathrm{3}\pi}{\mathrm{4}} \\ $$
Commented by bobhans last updated on 19/Sep/20
$${gave}\:{kudos}… \\ $$
Commented by mohammad17 last updated on 19/Sep/20
$${thank}\:{you}\:{sir}\:{can}\:{you}\:{help}\:{me}\:{in}\:\left({B}\right)\:{please} \\ $$