The option(s) with the value of \(a\) and \(L\) that satisfy the following equation is(are)…

The option(s) with the value of \(a\) and \(L\) that satisfy the following equation is(are) \(\frac{\int_0^{4 \pi} e^t\left(\sin ^6 a t+\cos ^4 a t\right) d t}{\int_0^\pi e^t\left(\sin ^6 a t+\cos ^4 a t\right) d t}=L\) ?
  1. a=2, L= e4π-1eπ-1
  2. a=2, L= e4π+1eπ+1 
  3. a=4, L= e4π-1eπ-1
  4. a=4, L= e4π+1eπ+1

Solution

l=04πet sin62t+cos4 2tdt =   l1+l2 + l3 + l4  
Where l1=0πet sin62t+cos42tdt   and l2= π2πet sin62t+cos4 2t dt  and  l3=2π3πetsin62t+cos42tdt  and l4=3π4πetsin6 2t+cos4 2t dt
t=x+π
dt=dx
l2=0πex+π sin6 2x+cos4 2x dx= eπl1
t=2π+x
l3=e2πl1
l4=e3πl1
l=l1 1+eπ+e2π+e3π
ll1=e4π-1eπ-1
The same for a = 4.

Asked in: JEE Advanced 2015 (Paper 2)

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