<span> √2 cos (x- pi/4) = sin x + cos x</span>
Уравнение перепишется как sin x = sqrt(3)/2
x=(-1)^k * pi/3 + 2pik, k in Integers
<span>√2 sin (pi/4-x) = cos x - sin x</span>
<span>cos x = -1/2</span>
<span>x=+- 2pi/3+pi n, n in Integers</span>
<span><span>sin (45 градусов - a)=1/</span></span>√2*(cos x - sin x)
cos (x- pi/4) =1/√2(sin x + cos x)
Разделите друг на друга выражения и все получится.
A3=a1+2d=-5
a6=a1+5d=2.2
a6-a3=3d=2.2-(-5)=7.2
d=7.2/3=2.4
a1=a3-2d=-5-2*2.4=-9.8
S15=(a1+a15)/2*15
a15=a1+14d=-9.8+14*2.4=23.8
S15=(-9.8+23.8)/2*15=105
<span>0,3a(4a² - 3)(2a²+5)= 0,3а*(8а^4+20a</span>²-6a²-15<span>)=2,4a^5+4,2a</span>³-5a
решение:
(cos(135)sin(210) ÷(
· cos(405))
cos(135)sin(210)÷ ![\frac{sin(135)cos(405)}{cos(135)}](https://tex.z-dn.net/?f=%5Cfrac%7Bsin%28135%29cos%28405%29%7D%7Bcos%28135%29%7D)
cos(135)sin(210) · ![\frac{cos(135)}{sin(135)cos(405)}](https://tex.z-dn.net/?f=%5Cfrac%7Bcos%28135%29%7D%7Bsin%28135%29cos%28405%29%7D)
ответ:
![\frac{cos(135)}{sin(135)cos(405)}](https://tex.z-dn.net/?f=%5Cfrac%7Bcos%28135%29%7D%7Bsin%28135%29cos%28405%29%7D)
≈-5,44209