(u-v) (u^2-uv+v^2)=u^3-u^2v+uv^2-u^2v+uv^2-v^3=<span>u^3-2u^2v+2uv^2-v^3</span>
-х^2+4=0
-x^2=0-4
-x^2=-4
x=-4:(-2)
х=2
б)
![cos(2arctg1)](https://tex.z-dn.net/?f=cos%282arctg1%29)
arctg1 - это значение угла, при котором тангенс равен 1
![arctg1 = \frac{\pi}{4}](https://tex.z-dn.net/?f=arctg1+%3D+%5Cfrac%7B%5Cpi%7D%7B4%7D)
Проверим это
![tg\frac{\pi}{4} = \frac{sin\frac{\pi}{4}}{cos\frac{\pi}{4}} = \frac{\sqrt2}{2} \div \frac{\sqrt2}{2} = \frac{\sqrt2}{2} * \frac{2}{\sqrt2} = 1](https://tex.z-dn.net/?f=tg%5Cfrac%7B%5Cpi%7D%7B4%7D+%3D+%5Cfrac%7Bsin%5Cfrac%7B%5Cpi%7D%7B4%7D%7D%7Bcos%5Cfrac%7B%5Cpi%7D%7B4%7D%7D+%3D+%5Cfrac%7B%5Csqrt2%7D%7B2%7D+%5Cdiv+%5Cfrac%7B%5Csqrt2%7D%7B2%7D+%3D+%5Cfrac%7B%5Csqrt2%7D%7B2%7D+%2A+%5Cfrac%7B2%7D%7B%5Csqrt2%7D+%3D+1)
![cos(2arctg1) = cos(2\cdot \frac{\pi}{4}) = cos\frac{\pi}{2} = 0](https://tex.z-dn.net/?f=cos%282arctg1%29+%3D+cos%282%5Ccdot+%5Cfrac%7B%5Cpi%7D%7B4%7D%29+%3D+cos%5Cfrac%7B%5Cpi%7D%7B2%7D+%3D+0)
в)
![ctg(2arcsin\frac{1}{\sqrt2}) = ctg(2 \underbrace { arcsin\frac{\sqrt2}{2}}_{\frac{\pi}{4}}}) = ctg(2\cdot\frac{\pi}{4}) = ctg\frac{\pi}{2} = 0](https://tex.z-dn.net/?f=ctg%282arcsin%5Cfrac%7B1%7D%7B%5Csqrt2%7D%29+%3D+ctg%282+%5Cunderbrace+%7B+arcsin%5Cfrac%7B%5Csqrt2%7D%7B2%7D%7D_%7B%5Cfrac%7B%5Cpi%7D%7B4%7D%7D%7D%29+%3D+ctg%282%5Ccdot%5Cfrac%7B%5Cpi%7D%7B4%7D%29+%3D+ctg%5Cfrac%7B%5Cpi%7D%7B2%7D+%3D+0)
г)
![cos(\underbrace{arccos(-\frac{1}{2})}_{\pi-arccos(\frac{1}{2})}+\frac{\pi}{3}) = cos(\pi - \frac{\pi}{3}+\frac{\pi}{3}) = cos\pi = -1](https://tex.z-dn.net/?f=cos%28%5Cunderbrace%7Barccos%28-%5Cfrac%7B1%7D%7B2%7D%29%7D_%7B%5Cpi-arccos%28%5Cfrac%7B1%7D%7B2%7D%29%7D%2B%5Cfrac%7B%5Cpi%7D%7B3%7D%29+%3D+cos%28%5Cpi+-+%5Cfrac%7B%5Cpi%7D%7B3%7D%2B%5Cfrac%7B%5Cpi%7D%7B3%7D%29+%3D+cos%5Cpi+%3D+-1)
Ответ:
Объяснение:
sina=-√(1-cosa)=-√(1-9/25)=-4/5
Расстояние между А и Б =Sскорость велосипедиста vскорость мотоциклиста 9vза одно и тоже время tвелосипедист проехал S-16 кммотоциклист S км t=(S-16)v = S/(9v)(S-16)v = S/(9v)S-16= S/99(S-16)= S9S-16*9=S8S=16*9S=18 км