Prove that, \(\displaystyle{\left[{{\sin}^{{{n}+{1}}}{\left({x}\right)}}\right]}^{{2}}+{\left[{{\cos}^{{{n}+{1}}}{\left({x}\right)}}\right]}^{{2}}\geq{\left({\frac{{{1}}}{{{2}}}}\right)}^{{n}}\) where x is real and

Beryneingmk39

Beryneingmk39

Answered question

2022-03-30

Prove that,
[sinn+1(x)]2+[cosn+1(x)]2(12)n where x is real and n is a non-negative integer.

Answer & Explanation

Tristatex9tw

Tristatex9tw

Beginner2022-03-31Added 18 answers

use Holder inequality
[(cos2x)n+1+(sin2x)n+1][1+1]n(cos2x+sin2x)n+1=1
or Use AM-GM inequality we have
(sin2x)n+1+12n+1+12n+1++12n+1(n+1)n+112n(n+1)(sin2x)n+1=n+12nsin2x
so
(sin2x)n+1+n2n+1n+12n+1sin2x (1)
the same as
(cos2x)n+1+n2n+1n+12n+1cos2x (2)
(1)+(2)
sin2n+2x+cos2n+2x12n

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