The angle between the resultant contact force and the normal force exerted by a body on the other is called the angle of friction. Show that it `lamda` be the angle of friction and `mu` the coefficient of static friction. `lamdaletan^-1mu`.

Explanation

Let f be applied force
F be frictionl force and R be normal reaction

When `F=muR` is th limiting friction (max friction) when applined force increase, force of friction increase upto limiting friction (`muR)`
`Flt(muR)/F`
`:. tan lamda=F/RltmuR`
`rarr tan lamdaleu`
`rarr lamdaletan^-1mu`