Let y=f(x), f:R→R be an odd differentiable function such that f′′′(x)>0 and g(α,β)=sin8α+cos8β+2−4sin2αcos2β. If f′′(g(α,β))=0, then sin2α+sin2β is equal to
1
f′′(x) is odd function ⇒g(α,β)=0
⇒(sin4α−1)2+(cos4β−1)2+2(sin2α−cos2β)2=0
sin2α+sin2β=1