![sin( \frac{3 \pi }{2}+arccos \frac{1}{3} )= \\ = sin(\frac{3 \pi }{2})*cos(arccos \frac{1}{3})+cos(\frac{3 \pi }{2})*sin(arccos \frac{1}{3})= \\ =- \frac{1}{3} \\ sin(2arccos \frac{3}{5} )=2*sin(arccos \frac{3}{5})*cos(arccos \frac{3}{5})= \\ =2* \sqrt{1- \frac{9}{25} } * \frac{3}{5} = \frac{6}{5} * \frac{4}{5} = \frac{24}{25} =0.96](https://tex.z-dn.net/?f=sin%28+%5Cfrac%7B3+%5Cpi+%7D%7B2%7D%2Barccos+%5Cfrac%7B1%7D%7B3%7D+%29%3D+%5C%5C+%3D+sin%28%5Cfrac%7B3+%5Cpi+%7D%7B2%7D%29%2Acos%28arccos+%5Cfrac%7B1%7D%7B3%7D%29%2Bcos%28%5Cfrac%7B3+%5Cpi+%7D%7B2%7D%29%2Asin%28arccos+%5Cfrac%7B1%7D%7B3%7D%29%3D+%5C%5C+%0A%3D-+%5Cfrac%7B1%7D%7B3%7D++%5C%5C+%0Asin%282arccos+%5Cfrac%7B3%7D%7B5%7D+%29%3D2%2Asin%28arccos+%5Cfrac%7B3%7D%7B5%7D%29%2Acos%28arccos+%5Cfrac%7B3%7D%7B5%7D%29%3D+%5C%5C+%0A%3D2%2A+%5Csqrt%7B1-+%5Cfrac%7B9%7D%7B25%7D+%7D+%2A+%5Cfrac%7B3%7D%7B5%7D+%3D+%5Cfrac%7B6%7D%7B5%7D+%2A+%5Cfrac%7B4%7D%7B5%7D+%3D+%5Cfrac%7B24%7D%7B25%7D+%3D0.96)
cos(arccos(a))=a
sin(arccos(a))=√(1-a²)
cos(arcsin(a))=√(1-a²)
sin(2a)=2sin(a)cos(a)
sin(a+b)=sin(a)*cos(b)+cos(a)sin(b).
Ctg135°=-1 если не ошибаюсь
1. 2у + у(3 – (у + 1)) = у(2 – у) + 12
2у + у(3 – у - 1) = 2y - y² +12
2у + 3y - y² - y = 2y - y² +12
2у + 3y - y² - y - 2y + y² = 12
2y = 12
y = 12 : 2
y = 6
2. 7 + 3(- х – 3(х + 5)) = 5(7 –
2х) + х
7 + 3(- х – 3х - 15) = 35 - 10x + x
7 - 3x - 9x - 45 = 35 - 10x + x
10x - x - 3x - 9x = 35 - 7 + 45
-3x = 73
-x = 73 : 3
-x ≈ 24,3
x ≈ - 24,3
X-2y=6
-2y=6-x
2y=6+x
y=3+x/2
или вот так
<span>у = (х - 6)/2 </span>
Решение: 40:2 = 20 BC=CD
20/2 = 10 AB=CD
S=2(a+b)
S=2(10м+20м) = 60м ^2