Sunil Raikwar
Last Activity: 11 Years ago
we know that f(x) is decreasing for all real values of x if f'(x)<0
f'(x)=-cosx-sinx+a<0
a<sinx+cosx
minimum value of sinx+cosx is -root2
so a should be less than -root2
Thanks & Regards
Sunil Raikwar
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