Given,
f(x)=xloge(1234)−(tan1∘)(tan1∘)x+loge(123),x>0
Now, let tan1∘=a,loge(123)=b and loge(1234)=c
So, f(x)=cx−aax+b
⇒f(f(x))=cf(x)−aaf(x)+b
⇒f(f(x))=c(cx−aax+b)−aa(cx−aax+b)+b
⇒f(f(x))=acx+bc−a(cx−a)a2x+ab+b(cx−a)=bc+a2a2x+bcx=x
⇒f(f(x))+f(f(x4))=x+x4
∵x>0, then least value =x⋅x4=2