Вычислите значение выражения 5ctg 13/2п+2cos 21п/4+2sin 41п/4

Решите задачу:

$5ctg\frac{13\pi}{2}+2cos \frac{21\pi}{4}+2sin\frac{41\pi}{4}\\ ctg\frac{13\pi}{2}=ctg(\frac{12\pi}{2}+\frac{\pi}{2})=ctg(6\pi+\frac{\pi}{2})=ctg\frac{\pi}{2}=0;\\ cos \frac{21\pi}{4}=cos(\frac{20\pi}{4}+\frac{\pi}{4})=cos(5\pi+\frac{\pi}{4})=-cos\frac{\pi}{4}=-\frac{\sqrt2}{2};\\ sin\frac{41\pi}{4}=sin(\frac{40\pi}{4}+\frac{\pi}{4})=sin(10\pi+\frac{\pi}{4})=sin\frac{\pi}{4}=\frac{\sqrt2}{2};\\5*0+2*(-\frac{\sqrt2}{2})+2*\frac{\sqrt2}{2}=-\sqrt2+\sqrt2=0.$