安装juliazh后依然是英文文档，版本1.5.3，win10

[zhanghg1983]

help?> cos
search: cos cosh cosd cosc cospi acos acosh acosd sincos sincosd const close isconst copysign MathConstants coalesce

cos(x)

Compute cosine of x, where x is in radians.

────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

cos(A::AbstractMatrix)

Compute the matrix cosine of a square matrix A.

If A is symmetric or Hermitian, its eigendecomposition (eigen) is used to compute the cosine. Otherwise, the cosine
is determined by calling exp.

Examples
≡≡≡≡≡≡≡≡≡≡

julia> cos(fill(1.0, (2,2)))
2×2 Array{Float64,2}:
0.291927 -0.708073
-0.708073 0.291927