Problem $6$: FCC Slip plane

Consider a single crystal of silver $($FCC$)$ oriented such that a tensile stress is applied along a $[001]$ direction. Slip occurs on a $(111)$ plane and in a $[101]$ direction.

a$.$ Compute the two angles phi$\_(1)($angle between tensile stress direction and normal of the slip plane$)$ and phi$\_(2)($angle between tensile stress direction and the slip direction$).$ Hint: the angle

between two vectors can be defined using the dot product $|$a$||$b$|$cos$($phi$)=$a$*$b

b$.$ If slip is initiated at an applied tensile stress of $1\mathrm{.}1$ MPa $,$ compute the critical resolved shear stress