Ta tinh dk $AC=6\sqrt{2}=CB va OB=6$Goi khoang cach tu M den A va B la $d_{1}$ va khoang cach tu C den M la $d_{2}$Pt do 2 song tu A va B gui toi M la $u_{AM}=u_{BM}=2a.cos(wt-\frac{2\pi d_{1}}{\lambda })$Pt do song tu C gui toi M la $u_{CM}=a.cos(wt-\frac{2\pi d_{2}}{\lambda })$De M dao dong vs bien do la $5a=2a+2a+a$ thi cac song tu nguon truyen toi M cung phaKhi do $\frac{2\pi (d_{1}-d_{2})}{\lambda }=k2\pi $De OM min thi $d_{1}-d_{2}=\lambda =1,2$Khi do $\sqrt{x^{2}+OB^{2}}-(CO-x)=1,2$ vs $OM=x$ $\sqrt{x^{2}+36}-(6-x)=1,2$ De dang tinh dk $x=1,1cm$Dap an $A$
Ta tinh dk $AC=6\sqrt{2}=CB va OB=6$Goi khoang cach tu M den A va B la $d_{1}$ va khoang cach tu C den M la $d_{2}$Pt do 2 song tu A va B gui toi M la $u_{AM}=u_{BM}=2a.cos(wt-\frac{2\pi d_{1}}{\lambda })$Pt do song tu C gui toi M la $u_{CM}=a.cos(wt-\frac{2\pi d_{2}}{\lambda })$De M dao dong vs bien do la $5a=2a+2a+a$ thi cac song tu nguon truyen toi M cung phaKhi do $\frac{2\pi (d_{1}-d_{2})}{\lambda }=k2\pi $De OM min thi $d_{1}-d_{2}=\lambda =1,2$Khi do $\sqrt{x^{2}+OB^{2}}-(CO-x)=1,2$ vs $OM=x$ $\sqrt{x^{2}+36}-(6-x)=1,2$ De dang tinh dk $x=1,1cm$Dap an $C$
Ta tinh dk $AC=6\sqrt{2}=CB va OB=6$Goi khoang cach tu M den A va B la $d_{1}$ va khoang cach tu C den M la $d_{2}$Pt do 2 song tu A va B gui toi M la $u_{AM}=u_{BM}=2a.cos(wt-\frac{2\pi d_{1}}{\lambda })$Pt do song tu C gui toi M la $u_{CM}=a.cos(wt-\frac{2\pi d_{2}}{\lambda })$De M dao dong vs bien do la $5a=2a+2a+a$ thi cac song tu nguon truyen toi M cung phaKhi do $\frac{2\pi (d_{1}-d_{2})}{\lambda }=k2\pi $De OM min thi $d_{1}-d_{2}=\lambda =1,2$Khi do $\sqrt{x^{2}+OB^{2}}-(CO-x)=1,2$ vs $OM=x$ $\sqrt{x^{2}+36}-(6-x)=1,2$ De dang tinh dk $x=1,1cm$Dap an $
A$