Hello,
I've run into a problem with the SubstEquiv answer test and I am not sure if the test is not working as intended or if I am misunderstanding how it is supposed to work.
Consider a simple example where the correct answer is
A*sin(x) + B*cos(x)
I want the names of the coefficients A and B to be able to be chosen freely, whereas the argument x must be written as x. So, in the prt I choose SubstEquiv as the answer test and set the test option as [x]. If one now gives the answer
C*sin(x) + D*cos(x)
or
B*sin(x) + A*cos(x)
these are deemed correct with the expected substitutions [C = A, D = B] and [B = A, A = B], respectively. So far so good.
However, if one gives the answer
A*sin(z) + B*cos(z)
it is still counted as the correct answer with the substitution [z = x]. But shouldn't exactly this be counted wrong as per the test options, fixing x as x? Is there a way to enforce that the argument of sin and cos must be written as x?
Help would be much appreciated.