已知向量a=(1,1),b=(1,0),c满足a?c等于0,且|a|=|c|,b?c＞0.

(1) |a| = √2 let c=(x,y) => x^2 +y^2 =2 (1) a.c =0 (1,1)(x,y) =0 => x+y = 0 (2) b.c >0 (1,0)(x,y)>0 => x > 0 sub (2) into (1) 2x^2 = 2 x = 1 or -1( rejected , x>0) y = -1 c ( 1,-1) (2) f:(x