The angle of repose:- it is the minimum angle that an inclined plane makes with the horizontal when a body placed on it just begins to slide down.
let any inclined plane inclined with θ angle with horizontal and a body which mass is m just begins to slide down.
then,
mg.sinθ=μN
where μ is the coefficient of friction and N is the normal reaction.
N=mg.cosθ
now,
mg.sinθ=μmg.cosθ
tanθ=μ
θ=tan−1(μ)
here θ is known as angle of repose.