Answer / ajay pilassery

P.f = cosø
bcz, p.f=true powr/ apparent powr;
i.e, true powr=VI Cosø &apprnt powr=VI. So, = VI COSø/VI.
I.e, p.f=cosø. Its only cosin angle

The product of VI COSØ is the true powr & is measured in watts(using wattmeters). So, the product VI is apprnt powr measured in volt-ampere., Like V*I in watts , (using voltmeter&ammeter)

Answer / brd ganesh

Let assume pi=0 cos(0)=1 it means there phase
angle(pi) is 0 then p=vicos
(pi)=vi*1=vi take a
sin instead of cos sin(0)=0 then p=visin(pi)=vi*0=0
that is why choose cos

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