return values of sin and cos

[stevengj]

This seems inconsistent:

julia> cos(A)
4×4 Symmetric{Float64, Matrix{Float64}}:
 36765.0    36532.0    10744.7      537.235
 36532.0    41062.9    -5909.58    8595.76
 10744.7    -5909.58   60940.6   -27936.2
   537.235   8595.76  -27936.2    13663.9

julia> sin(A)
4×4 Matrix{Float64}:
      0.0   13228.5  -46097.2          22406.2
 -13228.5       0.0  -49673.4          22070.7
  46097.2   49673.4       1.81899e-12   7221.87
 -22406.2  -22070.7   -7221.87             5.68434e-14

julia> cosh(A)
4×4 Hermitian{Float64, Matrix{Float64}}:
 0.766512      0.0374       0.011        0.000550001
 0.0374        0.770912    -0.00605001   0.00880001
 0.011        -0.00605001   0.791262    -0.0286
 0.000550001   0.00880001  -0.0286       0.742862

julia> sinh(A)
4×4 SkewHermitian{Float64, Matrix{Float64}}:
  0.0       -0.167402  0.555537   0.272569
  0.167402   0.0       0.183709  -0.585157
 -0.555537  -0.183709  0.0       -0.174807
 -0.272569   0.585157  0.174807   0.0

Why doesn't cos return Hermitian and sin return SkewHermitian?

[stevengj]

Similarly for tan and tanh and the other trig functions.

[smataigne]

I solved this issue in #109