limn→∞sin(a2n)sin(b2n)
=limn→∞sin(a2n)sin(b2n)
=n→∞, Let 1n⇒h→0
=limh→0⎛⎜⎝a21h⎞⎟⎠limh→0⎛⎜⎝b21h⎞⎟⎠
=⎛⎜ ⎜ ⎜ ⎜⎝limh→0sina21ha21h×a21h⎞⎟ ⎟ ⎟ ⎟⎠⎛⎜ ⎜ ⎜ ⎜ ⎜⎝limh→0sinb21hb21h×b21h⎞⎟ ⎟ ⎟ ⎟ ⎟⎠
=1×a1×b=ab