![\frac{1}{\sqrt{10} } * sin \frac{x}{2}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7B%5Csqrt%7B10%7D+%7D+%2A+sin+%5Cfrac%7Bx%7D%7B2%7D)
, cos x = -0,8, x ∈ (π; 3π/2)
![sin \frac{x}{2}](https://tex.z-dn.net/?f=sin+%5Cfrac%7Bx%7D%7B2%7D)
= (+/-)
![\sqrt{ \frac{1-cosx}{2} }](https://tex.z-dn.net/?f=+%5Csqrt%7B+%5Cfrac%7B1-cosx%7D%7B2%7D+%7D+)
x/2 ∈ (π/2; 3π/4) ⇒ угол x/2 лежит во II четверти ⇒
![sin \frac{x}{2}](https://tex.z-dn.net/?f=sin+%5Cfrac%7Bx%7D%7B2%7D)
> 0 ⇒
![sin \frac{x}{2}](https://tex.z-dn.net/?f=sin+%5Cfrac%7Bx%7D%7B2%7D)
=
![\sqrt{ \frac{1-cosx}{2} }](https://tex.z-dn.net/?f=%5Csqrt%7B+%5Cfrac%7B1-cosx%7D%7B2%7D+%7D+)
Окончательно:
![\frac{1}{\sqrt{10} } * sin \frac{x}{2}=\frac{1}{\sqrt{10}}*\sqrt{ \frac{1-cosx}{2} }=\sqrt{ \frac{1-cosx}{20}}=\sqrt{ \frac{1-(-0,8)}{20}}=\sqrt{ \frac{1,8}{20}}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7B%5Csqrt%7B10%7D+%7D+%2A+sin+%5Cfrac%7Bx%7D%7B2%7D%3D%5Cfrac%7B1%7D%7B%5Csqrt%7B10%7D%7D%2A%5Csqrt%7B+%5Cfrac%7B1-cosx%7D%7B2%7D+%7D%3D%5Csqrt%7B+%5Cfrac%7B1-cosx%7D%7B20%7D%7D%3D%5Csqrt%7B+%5Cfrac%7B1-%28-0%2C8%29%7D%7B20%7D%7D%3D%5Csqrt%7B+%5Cfrac%7B1%2C8%7D%7B20%7D%7D)
= 0,3
15/(x-1.5)-18/(x+1.5)=0.5
(15/(x-1.5)-18/(x+1.5))*(x-1.5)=0.5*(x-1.5)
(-6x+99)/(2x+3)=0.5x-0.75
(-6x+99)/(2x+3)*(x+1.5)=(0.5x-0.75)*(x+1.5)
-3x+49.5=0.5x²-1.125
-0.5x²-3x+50,625=0
x1=-13.5 x2=7.5
7.5+1.5=9
7.5-1.5=6
18/9=2
15/6=2.5
2.5-2=0.5
15/(x-1.5)-18/(x+1.5)=0.5
-0.5x²-3x+50,625=0
x1=-13.5
x2=7.5
Ответ: 7,5 км в час
∫dx/e^3x=∫e^(-3x)dx
u=3x
∫1/3*e^(-u)=1/3∫e^(-u)
v=e^(u)
1/3∫v^(-2)dx=-1/3v+C=-1/3e^(3x)+C
Ответ:
Объяснение:
решение на фото..........................