# Question:how to avoid this error message ?

## Question:how to avoid this error message ?

Maple 2018
f := proc (a, b) options operator, arrow; (1/2)*b+(1/2)*arccos(sin(2*a-b)/tan(b)) end proc; dis := proc (A, B) options operator, arrow; sqrt(inner(A-B, A-B)) end proc; bisA := proc (A, B, C) local b, c, M; b, c := dis(A, C), dis(A, B); M := (b*B+C*c)/(b+c); x*(A[2]-M[2])+y*(M[1]-A[1])+A[1]*M[2]-A[2]*M[1] end proc; P := proc (a0, b0) local a, b, c, p1, p2, p3, p4, r, II; a := evalf(a0); b := evalf(b0); c := f(a, b); if b0-0.1e-2 < a0 then return plot() end if; p1, p2, p3, p4 := [1, 0], [cos(4*a), sin(4*a)], [cos(4*b), sin(4*b)], [cos(4*c), sin(4*c)]; II := eval([x, y], solve([bisA(p2, p1, p3), bisA(p3, p2, p4)])); r := evalf(eval(dis(II, p2)*cos(b))); plots:-display(plot([p1, p2, p3, p4, p1]), plottools:-circle(II, r, color = blue), plottools:-circle([0, 0], 1)) end proc; Explore(P(a, b), parameters = [a = 0.1e-1 .. (1/2)*Pi-0.2e-1, b = 0.2e-1 .. (1/2)*Pi-0.1e-1], initialvalues = [a = (1/8)*Pi, b = (1/4)*Pi]); Error, invalid input: Explore expects value for keyword parameter initialvalues to be of type {NoUserValue, list(name = anything)}, but received [5 = (1/8)*Pi, 11 = (1/4)*Pi Thank you.
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