A AB = 10 см
Cos<B = 0,6
BC = ?
C B
Косинусом острого угла называется отношение прилежащего катета к гипотенузе
![Cos\ \textless \ B = \frac{BC}{AB} \\\\BC = AB * Cos\ \textless \ B = 10*0,6 = 6](https://tex.z-dn.net/?f=Cos%5C+%5Ctextless+%5C+B+%3D++%5Cfrac%7BBC%7D%7BAB%7D+%5C%5C%5C%5CBC+%3D+AB+%2A+Cos%5C+%5Ctextless+%5C+B+%3D+10%2A0%2C6+%3D+6)
см
![\frac{x-1}{x+3} + \frac{28}{(x+3)(x-4)} = \frac{3x}{x-4} \\ \\ \frac{x-1}{x+3} + \frac{28}{(x+3)(x-4)} - \frac{3x}{x-4}=0 \\ \\ \frac{(x-1)(x-4)+28-3x(x+3)}{(x+3)(x-4)}=0 \\ \\ \frac{x^2-5x+4+28-3x^2-9x}{(x+3)(x-4)}=0 \\ \\ \left \{ {{-2x^2-14x+32=0} \atop {(x+3)(x-4) \neq 0}} \right.](https://tex.z-dn.net/?f=+%5Cfrac%7Bx-1%7D%7Bx%2B3%7D+%2B+%5Cfrac%7B28%7D%7B%28x%2B3%29%28x-4%29%7D+%3D+%5Cfrac%7B3x%7D%7Bx-4%7D++%5C%5C++%5C%5C++%5Cfrac%7Bx-1%7D%7Bx%2B3%7D+%2B+%5Cfrac%7B28%7D%7B%28x%2B3%29%28x-4%29%7D+-+%5Cfrac%7B3x%7D%7Bx-4%7D%3D0+%5C%5C++%5C%5C++%5Cfrac%7B%28x-1%29%28x-4%29%2B28-3x%28x%2B3%29%7D%7B%28x%2B3%29%28x-4%29%7D%3D0+%5C%5C++%5C%5C++%5Cfrac%7Bx%5E2-5x%2B4%2B28-3x%5E2-9x%7D%7B%28x%2B3%29%28x-4%29%7D%3D0+%5C%5C++%5C%5C++%5Cleft+%5C%7B+%7B%7B-2x%5E2-14x%2B32%3D0%7D+%5Catop+%7B%28x%2B3%29%28x-4%29+%5Cneq+0%7D%7D+%5Cright.+)
х≠-3; х≠4
x^2+7x-16=0
D=49+64=113
x=(-7-√113)/2 или х=(-7+√113)/2
О т в е т.(-7-√113)/2 или х=(-7+√113)/2
![\frac{2x}{x+2} - \frac{x-1}{x-3} = \frac{10}{(x-3)(x+2)} \\ \\ \frac{2x(x-3)-(x-1)(x+2)}{(x-3)(x+2)}= \frac{10}{(x-3)(x+2)} \\ \\ \frac{2x^2-6x-x^2-x+2}{(x-3)(x+2)}= \frac{10}{(x-3)(x+2)} \\ \\ \left \{ {{x^2-7x+2=10} \atop {(x-3)(x+2) \neq 0}} \right.](https://tex.z-dn.net/?f=%5Cfrac%7B2x%7D%7Bx%2B2%7D+-+%5Cfrac%7Bx-1%7D%7Bx-3%7D+%3D+%5Cfrac%7B10%7D%7B%28x-3%29%28x%2B2%29%7D+%5C%5C+%5C%5C+%5Cfrac%7B2x%28x-3%29-%28x-1%29%28x%2B2%29%7D%7B%28x-3%29%28x%2B2%29%7D%3D+%5Cfrac%7B10%7D%7B%28x-3%29%28x%2B2%29%7D+%5C%5C++%5C%5C++%5Cfrac%7B2x%5E2-6x-x%5E2-x%2B2%7D%7B%28x-3%29%28x%2B2%29%7D%3D+%5Cfrac%7B10%7D%7B%28x-3%29%28x%2B2%29%7D+%5C%5C++%5C%5C+++%5Cleft+%5C%7B+%7B%7Bx%5E2-7x%2B2%3D10%7D+%5Catop+%7B%28x-3%29%28x%2B2%29+%5Cneq+0%7D%7D+%5Cright.+)
х≠3; х≠-2
x²-7x-8=0
В=49+32=81
х=(7-9)/2=-1 или х=(7+9)/2=8
О т в е т. -1; 8