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Answer 1 · 2016-10-04T16:36:03

The function representing the variation of voltage with time is given by

$V(t)=60sin(2t+0.8)," where "t>=0$

(a) As it is a sine function , It will have

(1) a maximum value
when $sin(2t+0.8)$ is maximum = 1
So maximum value $V(t)=60V$

(2) a minimum value
when $sin(2t+0.8)$ is maximum =-1

So minimum value $V(t)=-60V$

(b) we are to findout the time when first time $V(t)=30V$

So putting $V(t)=30V$ we get

$30=60sin(2t+0.8)$

$=>sin(2t+0.8)=30/60=1/2=sin(pi/6)$

$=>2t=pi/6-0.8$

$=>2t=3.14/6=-0.8<0->"not possible"$

So taking

$sin(2t+0.8)=sin(pi-pi/6)$

$=>2t=(5pi)/6=-0.8=(5xx3.14)/6-0.8$

$=>2t=1.82$

$t=0.91s$

Hence first time at 0.91s $V(t)$ will reach to 30V value