Toán Lớp 10: Cho hình vuông ABCD cạnh a
tính (vecAD+vecAC)(vecBD+vecBC)
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 10: Cho hình vuông ABCD cạnh a
tính (vecAD+vecAC)(vecBD+vecBC)
Comments ( 1 )
\left(\overrightarrow{AD} +\overrightarrow{AC}\right)\left(\overrightarrow{BD}+\overrightarrow{BC}\right)\\
= \overrightarrow{AD}.\overrightarrow{BD} + \overrightarrow{AD}.\overrightarrow{BC} + \overrightarrow{AC}.\overrightarrow{BD} + \overrightarrow{AC}.\overrightarrow{BC}\\
= AD.BD.\cos\widehat{ADB} + AD.BC.\cos0^\circ + 0 + AC.BC.\cos\widehat{ACB}\\
= a.a\sqrt2.\cos45^\circ + a.a + a\sqrt2.a.\cos45^\circ\\
= a^2 + a^2 a^2\\
= 3a^2
\end{array}\)