关于符号求解方程的问题

Question

r1 = {l1/2 Sin[\[Theta]1], l1/2 Cos[\[Theta]2]}

r2 = {l1 Sin[\[Theta]1] + l2/2 Sin[\[Theta]2],
  l1 Cos[\[Theta]1] + l2/2 Cos[\[Theta]2]}

r3 = {l1 Sin[\[Theta]1] + l2 Sin[\[Theta]2],
  l1 Cos[\[Theta]1] + l2 Cos[\[Theta]2]}

Q1 = m1*g*\!\(
\*SubscriptBox[\(\[PartialD]\), \(\[Theta]1\)]r1\) + m2*g*\!\(
\*SubscriptBox[\(\[PartialD]\), \(\[Theta]1\)]r2\) + F*\!\(
\*SubscriptBox[\(\[PartialD]\), \(\[Theta]1\)]r3\)

Q2 = m1*g*\!\(
\*SubscriptBox[\(\[PartialD]\), \(\[Theta]2\)]r1\) + m2*g*\!\(
\*SubscriptBox[\(\[PartialD]\), \(\[Theta]2\)]r2\) + F*\!\(
\*SubscriptBox[\(\[PartialD]\), \(\[Theta]2\)]r3\)

Reduce[{Q1 == 0, Q2 == 0, m1 != 0, m2 != 0, g != 0, l1 != 0, l2 != 0,
  F != 0}, {\[Theta]1, \[Theta]2}]

为什么解不出来？求教

Answer 1

最后的Reduce，可以这样写：

Reduce[{Q1 == 0, Q2 == 0, m1 != 0, m2 != 0, g != 0, l1 != 0, l2 != 0, 
  F != 0}, {\[Theta]1, \[Theta]2, g, m1, m2, l1, l2, F}]