2014.05.18


              r2 /y2    enu: experience shows that relations between r,x,y
                / |          are independent of their values,  instead
               /  |
              /   |          here are some (named) relations
             /    |          cos=x/r -> x=cos*r, r=x/cos
            /     |          sin=y/r -> y=sin*r, r=y/sin
           /      |          ctg=x/y -> x=ctg*y, y=x/ctg
          /       |           tg=y/x -> y= tg*x, x=y/ tg
         /        |
        /         |          now have a look at Pythagoras distance file, suppose r=1, then
    r1 /y1        |          1=cos^2+sin^2 -> cos=sqrt(1-sin^2), sin=sqrt(1-cos^2)
      / |         |          always try to simplify, we are working on relations, relax
     /  |         |          what did Pythagoras smoke/drink?
    /   |         |
   /    |         |          furthermore           cos sin
  /    90       90         ctg=cos/sin -> ctg*tg=---*---=1, ctg=1/tg, tg=1/ctg
 -----x1--------x2           tg=sin/cos           sin cos                              ...


                        rus:     r,x,y
                                 -  

                               () 
                             cos=x/r -> x=cos*r, r=x/cos
                             sin=y/r -> y=sin*r, r=y/sin
                             ctg=x/y -> x=ctg*y, y=x/ctg
                              tg=y/x -> y= tg*x, x=y/ tg

                                 Pythagoras,  r=1, 
                             1=cos^2+sin^2 -> cos=sqrt(1-sin^2), sin=sqrt(1-cos^2)
                              ,  , , , 
                                   ?

                                ..     cos sin
                             ctg=cos/sin -> ctg*tg=---*---=1, ctg=1/tg, tg=1/ctg
                              tg=sin/cos           sin cos                              ...
                                                             