Let f(x)=3 cosx + 4 sinx + 5
We know that,
−√32+42≤3cosx+4sinx≤√32+42
⇒−√9+16≤3cosx+4sinx≤√9+16
⇒−√25≤3cosx+4sinx≤√25
⇒−5≤3cosx+4sinx≤5
⇒−5+5≤3cosx+4sinx+5≤5+5
⇒0≤3cosx+4sinx+5≤10 Hence, minimum and maximum values of 3 cosx + 4 sinx +5 are 0 and 10 respectively.