y=V2+2= C va b cot g"o a+b be s26=-7 bc csc20 C be2 1 (a+b) +b) (a+b)sin0 (a+b)2 sin20 =0 a,=同=√2+2= b*c2 1 (a+b)2x3 18 如  2 2 2 2 2 a b cot g a b c v x y M + + =  +  =      = + = − + + = − + = − 0 sin 1 ( )sin ( ) csc ( ) csc ( ) 2 2 2 2 2 y a b bc a b c a b bc a b bc x        2 3 4 2 2 2 1 (a b) x b c aM a x y + = =  +  =  18