Question

Дана функция y=sinx+cosx,вычислите y'(p/4)

Answer 1

$y=sin x+cos x=\sqrt{2}(\frac{\sqrt{2}}{2}sinx+\frac{\sqrt{2}}{2}cos x)=\sqrt{2}(sin x cos \frac{\pi}{4}+sin \frac{\pi}{4}cos x)=\sqrt{2}sin (x+\frac{\pi}{4})$

$y'=(\sqrt{2}sin(x+\frac{\pi}{4}))'=\sqrt{2}*(sin(x+\frac{\pi}{4})'=\sqrt{2}*cos(x+\frac{\pi}{4})*(x+\frac{\pi}{4})'=\sqrt{2}*cos(x+\frac{\pi}{4})*1=\sqrt{2}cos(x+\frac{\pi}{4})$

$y'(\frac{\pi}{4})=\sqrt{2}cos(\frac{\pi}{4}+\frac{\pi}{4})=\sqrt{2}*cos \frac{\pi}{2}=\sqrt{2}*0=0$

либо так

$y'=(sin x+cos x)'=(sin x)'+(cos x)'=cos x+(-sin x)=cos x-sin x$

$y'(\frac{\pi}{4})=cos \frac{\pi}{4}-sin \frac{\pi}{4}=\frac{\sqrt{2}}{2}-\frac{\sqrt{2}}{2}$

ответ: 0

Answer 2

у'=cosx -sinx,

y'(π/4) = cos(π/4) -sin(π/4) = (√2÷2) - (√2÷2) =0.

ответ: 0.