Toán Lớp 10: Cho |$\overrightarrow{a}$|=3 ; |$\overrightarrow{b}$|=4
($\overrightarrow{a}$ ; $\overrightarrow{b}$)=$60^o$
Tính |3$\overrightarrow{a}$+2 $\overrightarrow{b}$|
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Toán Lớp 10: Cho |$\overrightarrow{a}$|=3 ; |$\overrightarrow{b}$|=4
($\overrightarrow{a}$ ; $\overrightarrow{b}$)=$60^o$
Tính |3$\overrightarrow{a}$+2 $\overrightarrow{b}$|
Comments ( 1 )
= 9a^2+4b^2+12.|\vec(a)|.|\vec(b)|.cos(\vec(a);\vec(b))
=9.3^2 + 2.4^2+12.3.2.cos60^0 =149
\Rightarrow |3\vec(a)+2\vec(b)| = \sqrt(149)