(1-log(7)28)(1-log(4)28)=? 18log(5) из 9 корней из 5=? log(4 корней из 6)6=?

=(1-log(7)7-log(7)4)(1-log(4)4-log(4)7)=(1-1-log(7)4)(1-1-log(47)= =-log(7)4*(-log(4)7)=1 =18log(5)√5+18log(5)9=18*0,5+18log(5)9=9+18log(5)9 =1/[log(6)4√6]=1/[log(6)4+log(6)√6]=1/[log(6)4+0,5]

cos(a)=ac/ab

 

ac=ab*cos(a)=5*0,8=4

 

bc^2=ab^2-ac^2

bc^2=5^2-4^2=25-16=9

dc=3