Respuesta :

we know that

cos 45°=√2/2------> equation 1

in the triangle 
cos 45°=m/(9√2)----> equation 2
equals 1 and 2
so
√2/2=m/(9√2)---> 9√2*(√2)=2*m-------> 9*2=2*m-------> m=9

the answer is
m=9 units