1.

Let f(x)=int_(0)^(x) (sint-cost)(e^t-2)(t-1)^3(t-1)^3(t-2)^5 dt , 0lt xle4 Then , the number of points where f(x) assumes local maximum value , is

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SOLUTION :We have`f(x)=oversetxunderset0int(sint-cost)(e^t-2)(t-1)^3(t-1)^3(t-2)^5 dt , 0lt xle4`
`rArr f'(x)=oversetxunderset0int(sint-cost)(e^t-2)(x-1)^3(x-2)^5,0ltxle4`
for local maximum or minimum , we must have
f'(x)=0
`rArr sinx-cosx=0,e^x-2=0,(x-1)^3=0,(x-2)^5=0`
`rArr tanx=1,e^x=2,x=1,2`
`rArr x=5/4,(5pi)/4,x=log_e2,x=1,2 "" [therefore0 lt xle 4]`
`rArrx=0.785,3.925,0.693,1,2`
The changes in SIGN s of f'(x) in the nieghbourhoods of these POINTS are shown in Fig.17.
CLEARLY `x=log_e2,pi/4 and (5pi)/4` are points of local maxima


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