TRONG KHÔNG GIAN OXYZ, CHO HAI VECTO AR(2;1; 0), BR(−1; 0; 2− ). KHI...

Câu 15: Trong không gian

Oxyz

,

cho hai vecto

^a

^r

(

^{2;1; 0}

)

^,

^b

^r

(

⁻

^{1; 0; 2}

⁻

)

^{. Khi đó,}

^cos

( )

^{a b}

^{r r}

^,

^b

^ằ

^ng

A.

^cos

^{a b}

^{r r}

^,

⁼

₂₅

²

^.

^B.

^cos

^{a b}

^{r r}

^,

^{= −}

₂₅

²

^.

^C.

^cos

^{a b}

^{r r}

^,

^{= −}

²

₅

^.

^D.

^cos

^{a b}

^{r r}

^,

⁼

²

₅

^.

x

y

z