Q.

Let f(x)=1+eln(lnx).  ln(k2+25)  and  g(x)=1|x|1. If  limx1(f(x))g(x)=k(2sin2α+3cosβ+5),k>0 and α,βR , then which of the following is(are) CORRECT? 

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a

The value of k is equal to 5

b

The value of sin10α+cos5βsin2α+cosβ  is equal to 1

c

cos2β+sin4α=2

d

sin2α>cosβ

answer is A, B, C.

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Detailed Solution

As limx1(1+lnx.ln(k2+25))1|x|1=limx1(1+lnx.ln(k2+25))1x1

=elimx1lnxln(k2+25)x1=eln(k2+25)=k2+25

k2+25=k(2sin2α+3cosβ+5)

2sin2α+3cosβ+5=k+25k

k+25k2k.25kk+25k10

But L.H. S.  10
So. both L.H.S. and R.H.S. should be equal to 10.
sin2α=1 and cosβ=1

Hence,  sin10α+cos5βsin2α+cosβ=1+11+1=1

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Let f(x)=1+eln(lnx).  ln(k2+25)  and  g(x)=1|x|−1. If  limx→1(f(x))g(x)=k(2sin2α+3cosβ+5),k>0 and α,β∈R , then which of the following is(are) CORRECT?