+ napply mk_magma
+ [ napply (counter_image … f Mb)
+ | #x; #y; nwhd in ⊢ (% → % → ?); *; #x0; *; #Hx0; #Hx1; *; #y0; *; #Hy0; #Hy1; nwhd;
+ napply ex_intro
+ [ napply (op … x0 y0)
+ | napply conj
+ [ napply op_closed; nassumption
+ | nrewrite < Hx1;
+ nrewrite < Hy1;
+ napply (mmprop … f)]##]
+nqed.
+*)
+
+ndefinition m_intersect: ∀A. magma A → magma A → magma A.
+ #A; #M1; #M2;
+ napply (mk_magma …)
+ [ napply (intersect_is_ext_morph ? M1 M2)
+ | #x; #y; nwhd in ⊢ (% → % → %); *; #Hx1; #Hx2; *; #Hy1; #Hy2;
+ napply conj; napply op_closed; nassumption ]
+nqed.
\ No newline at end of file