一條超難數學題!!!!!!!!!!!!

By " 旋轉 ", it should be taken to mean a complete revolution, i.e. a turn of 360 degrees. Therefore, after 2 revolutions (or " n " revolutions so long as n is a positive integer), P should remain in its original position and hence the answer is A.

There is nothing to do with whether PQRS is a triangular pyramid or the relative position of where the line AB cuts the plane PQR.

Assume the rotation is completely,
Let the incentre of triangle PQR be O,
Let the length of each side = a
in triangle PQR,
O is the center of the inscribed circle of triangle PQR,
extend PO to QR and the interception of them is M,
OM perpendicular to RQ ( tanger perp. radius)
RM = MQ (prop. of isos. triangle)
thus, O is also the centroid of the inscribed circle of triangle PQR,
the projection of S on plane PQR is O
SO perpendicular to plane PQR
thus, after two complete rotation, the new position is P

I THINK IT IS R

i think is Q

何謂「兩次旋轉」呢？數學不是文學，要講得清清楚楚才可以的

C)R
因為佢係一個正４面體, 所有面都係一樣
而S係 三角形PQR o既中心點
so 第一次轉, P會去左Q, Q會去左R then R會去左P
第二次轉 P會去左R 所以答案應該係 R

我認為, 應該是P.............