513:23+x + 513/23-x = 46
513(23-x) + 513(23+x) = 46(529-x^2)
11799-513x+11799+513x = 24334-26x^2
26x^2+1026x-736=0
D=b^2-4ac= 1026^2-4*26*(-736) = 1129220
x= (-b+-sqrt(D))/2a = (-1026 +- sqrt(1129220))/2*26 = 0.7047.. ; -40.166..
1+ctg2x=-1/sin2x
sin2x/sin2x + cos2x/sin2x + 1/ sin2x =0
sin2x+cos2x+1=0
cos^2 x - sin^2 x +2 sinxcosx+ cos^2x + sin^2x=0
2sinxcosx+2cos^2x=0
2cosx(sinx+1)=0
cosx=0
x=П/2 +Пn
sinx=-1
x= -- П/2 +Пn
Хг масса 10%
х*10/100+100*100/100=(х+100)*15/100
10х+10000=15х+1500
15х-10х=10000-1500
5х=8500
х=8500:5
х=1700г 10%