How can I evaluate the eigenvectors of a 2x2 Matrix with trig functions as entries? This is what I did: with(LinearAlgebra): K:=<<cos(theta)|sin(theta)>,<sin(theta)|-cos(theta)>>; Eigenvectors(K); Error, (in LinearAlgebra:-LA_Main:-Eigenvectors) expecting either Matrices of rationals, rational functions, radical functions, algebraic numbers, or algebraic functions, or Matrices of complex(numeric) values I'm wondering why cos(theta) shouldn't be an algebraic function ?? Assuming theta to be real I get the same.

Hello, in a differential equation (in Maple 10) a variable should be replaced by a constant K so that all differentiations of this variable should evaluate to zero. This is my code: constants:= constants, K: myDG1:= u(t) + diff(u(t),t)^2 + v(t)=0: subs(u(t)=K,myDG1); K+(diff(K, t))^2+v(t) = 0 Although I have already assigned K to be constant, Maple doesn't replace d/dt K by 0. Any help would be appreciated.