The beam of an x$-$ray tube of copper hits a crystal with $2$d$=3\mathrm{.}6$ x $\mathrm{}\mathrm{}10\; ^\; -10\mathrm{ }$m$.$ What is the wavelength of the x$-$ray if the reflection of $1$st order strikes at a glancing angle of θ $=22\mathrm{.}5$ degrees