SICP Exercise 1.3

Exercise 1.3.  Define a procedure that takes three numbers as arguments and returns the sum of the squares of the two larger numbers.

(define (ex3 x y z)
                     (cond
                       ((> y z x) ((define a x) (define b y) (+ (square a) (square b))))
                       ((> y x z) ((define a x) (define b y) (+ (square a) (square b))))
                       ((> z y x) ((define a x) (define b y) (+ (square a) (square b))))
                       ((> z x y) ((define a x) (define b y) (+ (square a) (square b))))
                       ((> x z y) ((define a x) (define b y) (+ (square a) (square b))))
                       ((> x y z) ((define a x) (define b y) (+ (square a) (square b)))))

I know I'm thinking about this the wrong way. My solution doesn't work.

OP here, figured out to find the smallest number next time I sat down. Thanks for all the examples though.

I got this:

(define (ex3 x y z)
  (cond ((< x (+ y z)) (sum-of-squares y z))
    ((< y (+ z x)) (sum-of-squares z x))
    ((< z (+ x y)) (sum-of-squares x y))))