只是打比方，意思说有时物理的数学形式会导出不make sense 的解。

Example

Given: side a = 20, side c = 24, and angle C = 40°. Angle A is desired.

Using the law of sines, we conclude that

${\displaystyle {\frac {\sin A}{20}}={\frac {\sin 40^{\circ }}{24}}.}$

${\displaystyle A=\arcsin \left({\frac {20\sin 40^{\circ }}{24}}\right)\approx 32.39^{\circ }.}$

Note that the potential solution A = 147.61^? is excluded because that would necessarily give A + B + C > 180^?.

https://en.wikipedia.org/wiki/Law_of_sines

 

所有跟帖： 

• 任何三角形钝角的对边大于另外两边，因为a<c所以角A不能大于90度 -fourwaves- ♂ (245 bytes) () 08/28/2016 postreply 18:53:31