Воспользовавшись тождеством
![\cos(\arcsin \eta)=\sqrt{1-\eta^2}](https://tex.z-dn.net/?f=%5Ccos%28%5Carcsin%20%5Ceta%29%3D%5Csqrt%7B1-%5Ceta%5E2%7D)
, получим что
![\cos(\arcsin \frac{4}{5} )= \sqrt{1-\bigg( \dfrac{4}{5}\bigg)^2 }= \dfrac{3}{5}](https://tex.z-dn.net/?f=%5Ccos%28%5Carcsin%20%5Cfrac%7B4%7D%7B5%7D%20%29%3D%20%5Csqrt%7B1-%5Cbigg%28%20%5Cdfrac%7B4%7D%7B5%7D%5Cbigg%29%5E2%20%7D%3D%20%5Cdfrac%7B3%7D%7B5%7D%20%20)
8-12+15x=2x-34
15x-2x=12-8-34
13x=30
x=30/13
167.
1) 1 - (√x)^3
2) (√a)^3 + 8
169.
2)(√a+√b)/(a√a + b√b) =(√a+√b)/((√a)^3 + (√b)^3) = (√a+√b)/(√a+√b)(a - √ab + b) = = 1/(a - √ab + b) = (a - √ab + b)^ -1
81x^2-18x+1=0
D=b^2-4ac
D=(-18)^2-4×81×1=324-324=0
x1;2= 18+0 18 1
---------- = ----------- = -----------
2×81 162 9