Question

У=2ctgX X=-п/4 найти производную в точках

Answer 1

$y=2\, ctgx\\\\y'=2\cdot (- \frac{1}{sin^2x} )=-\frac{2}{sin^2x}\\\\y'(-\frac{\pi}{4})=- \frac{2}{sin^2(-\frac{\pi}{4})} =- \frac{2}{\sqrt2/2} =-2\sqrt2$