我想上來板上問一個書本上的一段敘述
因為不知道怎麼證明
Let E denote the set of all rigid motions of the plane.
-> ->
Assume f( x ) >= 0 for all x belonging to R^2.
If f。T = f for every T beongings to E, f must be constant.
請問這段敘述該怎麼證明?
感謝幫忙
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