Revision history [back]

X, Y = var('x y')
eq = (Y == 90 + X)
# Properly prints [y == x + 90]
print(solve(eq,[Y]))
# Properly prints [x == y - 90]
print(solve(eq,[X]))

# Improperly adds an additional variable and gives a useless answer for the value of Y
# Prints: [x == r1 - 90, y == r1]
# This gets me no closer to solving for y; it might as well say y == y.
print(solve(eq,[X,Y]))

Why does this give me a meaningless answer for Y?

X, Y = var('x y')
eq = (Y == 90 + X)
# Properly prints [y == x + 90]
print(solve(eq,[Y]))
# Properly prints [x == y - 90]
print(solve(eq,[X]))

# Improperly adds an additional variable and gives a useless answer for the value of Y
Rather than printing what I expected: [x == y - 90, y == x + 90]
# Prints: It prints: [x == r1 - 90, y == r1]
# This gets me no closer to solving for y; it might as well say y == y.
print(solve(eq,[X,Y]))

Why does How can I get the result I expect out of this? In my actual usage, I could have 10+ unknowns, each of which I want the equations rearranged(solved) for those variables, that way I can fetch an equation for each one as needed, already solved for with just that one variable on the left hand side. If solve doesn't do this, what will? It seems like I should be able to do this give me a meaningless answer for Y?with one invocation.. but perhaps I'm mistaken.