1-cos^x/cosx-1+sin^2x/sinx=1-cosx-1+sinx=sinx-cosx
![2 {cos}^{2} x + \sqrt{2} sinx > 2 \\ 2 - 2 {sin}^{2} x + \sqrt{2}sin x - 2 > 0 \\ 2 {sin}^{2} x - \sqrt{2}sin < 0 \\ \sqrt{2} sinx( \sqrt{2} sinx - 1) < 0 \\ 0 < sinx < \frac{ \sqrt{2} }{2} \\ \\2\pi \times n < x < \frac{\pi}{4} + 2\pi \times n](https://tex.z-dn.net/?f=2+%7Bcos%7D%5E%7B2%7D+x+%2B++%5Csqrt%7B2%7D+sinx+%3E+2+%5C%5C+2+-+2+%7Bsin%7D%5E%7B2%7D+x+%2B++%5Csqrt%7B2%7Dsin+x+-+2+%3E+0+%5C%5C+2+%7Bsin%7D%5E%7B2%7D+x+-++%5Csqrt%7B2%7Dsin++%3C+0+%5C%5C++%5Csqrt%7B2%7D+sinx%28+%5Csqrt%7B2%7D+sinx+-+1%29+%3C+0+%5C%5C+0+%3C+sinx+%3C++%5Cfrac%7B+%5Csqrt%7B2%7D+%7D%7B2%7D++%5C%5C++%5C%5C2%5Cpi+%5Ctimes+n+%3C++x+%3C++%5Cfrac%7B%5Cpi%7D%7B4%7D++%2B+2%5Cpi+%5Ctimes+n)
3пи/4 + пи*n <х< пи + пи*n
A2=1=a1+d
1=-3+d
d=4
a8=a1+d(8-1)=-3+7d=-3+28=25
Подставим в выражение значения –0,9 вместо 'х' и 1 вместо 'y'.
15*(–0,9)*1 – 5*(–0,9) + 18*1 – 6 = 318
1) 15*(–0,9) = –13,5
2) –13,5*1 = –13,5
3) 5*(–0,9) = –4,5
4) 18*1 = 18
5) –13,5 – (–4,5) = –13,5 + 4,5 = –9
6) –9 + 18 = 9
7) 9 – 6 = 3