Question

Помогите, срочно нужна помощь N2!!!

Answer 1

1) ctg (13п/2)=ctg(12п/2 + п/2)=ctg(6п + п/2)=ctg п/2 =0

2) cos (21п/4) = cos(20п/4 + п/4)=cos(5п + п/4) = - cos п/4 = -√2/2

3) sin(41п/4)=sin(40п/4 + п/4)=sin(10п + п/4)=sin п/4= √2/2

4) 5*0+2*(-√2/2)+2*(√2/2)=0-√2+√2=0

Ответ: 0.

Answer 2

$5ctg \frac{13 }{2} \pi +2cos \frac{21 \pi }{4} +2sin \frac{41 \pi }{4} =$$=5ctg (6 \pi +\frac{ \pi }{2} ) +2cos(5 \pi + \frac{ \pi }{4}) +2sin (10 \pi +\frac{ \pi }{4})=$$=5ctg \frac{ \pi }{2} +2cos( \pi + \frac{ \pi }{4}) +2sin\frac{ \pi }{4}=5*0-2cos \frac{ \pi }{4}+2* \frac{ \sqrt{2} }{2}=$$=0-2* \frac{ \sqrt{2} }{2}+ \sqrt{2} =- \sqrt{2} + \sqrt{2} =0$