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Question Number 114514 by mohammad17 last updated on 19/Sep/20

Commented by bobhans last updated on 19/Sep/20

(B) u^→ .v^→  = ∣u^→ ∣.∣v^→ ∣ ⇔ cos α=1   α=0°

$$\left({B}\right)\:\overset{\rightarrow} {{u}}.\overset{\rightarrow} {{v}}\:=\:\mid\overset{\rightarrow} {{u}}\mid.\mid\overset{\rightarrow} {{v}}\mid\:\Leftrightarrow\:\mathrm{cos}\:\alpha=\mathrm{1} \\ $$$$\:\alpha=\mathrm{0}° \\ $$

Commented by mohammad17 last updated on 19/Sep/20

wow ! thank you sir

$${wow}\:!\:{thank}\:{you}\:{sir} \\ $$

Answered by bobhans last updated on 19/Sep/20

(A) a^→ .b^→  = ∣a^→ ×b^→ ∣   ∣a^→ ∣.∣b^→ ∣.cos α=∣a^→ ∣.∣b^→ ∣.sin α  → tan α=1 ; a=(π/4), ((3π)/4)

$$\left({A}\right)\:\overset{\rightarrow} {{a}}.\overset{\rightarrow} {{b}}\:=\:\mid\overset{\rightarrow} {{a}}×\overset{\rightarrow} {{b}}\mid\: \\ $$$$\mid\overset{\rightarrow} {{a}}\mid.\mid\overset{\rightarrow} {{b}}\mid.\mathrm{cos}\:\alpha=\mid\overset{\rightarrow} {{a}}\mid.\mid\overset{\rightarrow} {{b}}\mid.\mathrm{sin}\:\alpha \\ $$$$\rightarrow\:\mathrm{tan}\:\alpha=\mathrm{1}\:;\:{a}=\frac{\pi}{\mathrm{4}},\:\frac{\mathrm{3}\pi}{\mathrm{4}} \\ $$

Commented by bobhans last updated on 19/Sep/20

gave kudos...

$${gave}\:{kudos}... \\ $$

Commented by mohammad17 last updated on 19/Sep/20

thank you sir can you help me in (B) please

$${thank}\:{you}\:{sir}\:{can}\:{you}\:{help}\:{me}\:{in}\:\left({B}\right)\:{please} \\ $$

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