请教一道GWD数学

feliceyu

Q21:
A certain circle in the xy-plane has its center at the origin.  If P is a point on the circle, what is the sum of the squares of the coordinates of P?
(1)    The radius of the circle is 4.
(2)    The sum of the coordinates of P is 0.
   
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.
                                 Answer: A


谢了

feliceyu

没看懂问题，现在明白了。很感谢！

mydloveal

是问P点两个坐标的平方和对吧~~就是X^2+Y^2  因为圆心是原点，P在圆上，所以它的两个坐标都等于半径呀 条件1就行了

条件2只能说明P点在第2或第4象限而已