А∧-9/а-² х а∧-5 при а=1/2
а∧-9/а∧-7=а-² =1/а² при а=1/2 ВЫРАЖЕНИЕ РАВНО 1/4
Ответ (С)
3 I x+3I -I5x-2I=3
1. 3х+9 -5х+2=3
-2х=-11+3
х=4
2.-3х+9+5х-2=3
2х=-7+3
х=-2
Если sin a =0,6=3/5, то 3 - противолежащий катет, 5 - гипотенуза, 4 - прилежащий катет. Значит tg(180град.+a)=<span>tgа = 3/4=0,75.
Ответ: 0,75.</span>
ОДЗ
{x>0
{x≠1
x∈(0;1) U (1;∞)
log(x)9=log(3)9/log(3)x
log(x)9=2/log(3)x
log(3)x=1+2/log(3)x
log(3)x=a,
a=1+2/a
a²-a-2=0
a1+a2=1 U a1*a2=-2
a1=-1⇒log(3)x=-1⇒x=1/3
a2=2⇒log(3)x=2⇒x=9
Ответ x={1/3;9}
<span>Решение 12cos(5pi/12)-sqrt(3)=6+6cos(5pi/6)-sqrt(3)=6-6cos(pi/6)-sqrt(3)=6-6sqrt(3)/2-sqrt(3)=6-4sqrt(3)</span>
![-1 \leq cos(\alpha) \leq 1](https://tex.z-dn.net/?f=-1+%5Cleq+cos%28%5Calpha%29+%5Cleq+1)
- возможные значения косинуса
![2cos^2(x) - 5cos(x) + 3 = 0\\\\ 2cos^2(x) - 2cos(x)-3cos(x) + 3 = 0\\\\ 2cos(x)*(cos(x) - 1)-3*(cos(x) -1) = 0\\\\ (2cos(x) - 3)*(cos(x) -1) = 0\\\\ 2cos(x)-3=0\ \ or\ \ cos(x)-1=0\\\\ cos(x)=\frac{3}{2}\ \ or\ \ cos(x)=1\\\\ cos(x)=1\\\\ x=2\pi n,\ n\in Z](https://tex.z-dn.net/?f=2cos%5E2%28x%29+-+5cos%28x%29+%2B+3+%3D+0%5C%5C%5C%5C%0A2cos%5E2%28x%29+-+2cos%28x%29-3cos%28x%29+%2B+3+%3D+0%5C%5C%5C%5C%0A2cos%28x%29%2A%28cos%28x%29+-+1%29-3%2A%28cos%28x%29+-1%29+%3D+0%5C%5C%5C%5C%0A%282cos%28x%29+-+3%29%2A%28cos%28x%29+-1%29+%3D+0%5C%5C%5C%5C%0A2cos%28x%29-3%3D0%5C+%5C+or%5C+%5C+cos%28x%29-1%3D0%5C%5C%5C%5C%0Acos%28x%29%3D%5Cfrac%7B3%7D%7B2%7D%5C+%5C+or%5C+%5C+cos%28x%29%3D1%5C%5C%5C%5C%0Acos%28x%29%3D1%5C%5C%5C%5C%0Ax%3D2%5Cpi+n%2C%5C+n%5Cin+Z)
Ответ:
![2\pi n,\ n\in Z](https://tex.z-dn.net/?f=2%5Cpi+n%2C%5C+n%5Cin+Z)