A:Answer I'm not clear on what you are asking; "can you use this tv as monitor for a tv ?"
If the question is, "Can this TV be used as a monitor for a computer?", then the answer is wholly dependent upon what type of cabling you intend to employ. There are input jacks for HDMI, coaxial cable, RCA-type components, composite, USB and ethernet.
If the question is, "Can this TV be used as a monitor for Sling, AppleTV, Amazon FireTV, etc.?", then the answer is yes.