Comments by "Fhf Fhf" (@fhffhff) on "The Curious" channel.

  1. √(R²-(R-1)²)+2=R,√(2R-1)=R-2,{2R=R²-4R+ 4,R-2»0;{-R²+6R-4=0,R»2;{R=(-6±√(36-4*-1 *-4))/-2,R≥2;{[R=3+√5,R=3-√5;R≥2;R=3+ √5.
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  2. cos(xy)(y+xy')=-sin(x+y)(1+y'),y'=(-ycos(x y)-sin(x+y))/(xcos(xy)+sin(x+y))
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  3. πR²-πr²=π(h²+2²-h²-1²)=3π
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  4. cosyy'-sinx=0,y'=sinx/cosy
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  5. (1+n)/2*n*(π/n)²=π²(1+n)/2/n=π²/2
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