運算式 8: "y" equals "x" times tangent left parenthesis, StartFraction, 2 pi Over 5 , EndFraction , right parenthesisy=x·tan2π5
8
A little trig shows the length of that hypotenuse is then just
9
運算式 10: secant left parenthesis, StartFraction, 2 pi Over 5 , EndFraction , right parenthesissec2π5
10
Alright, we're ready to graph this in one function! Turn off all of the above. Then Define our f(x) (don't graph it):
11
運算式 12: "f" left parenthesis, "x" , right parenthesis equals StartFraction, 1 Over cos left parenthesis, "x" plus StartNestedFraction, 2 pi NestedOver 5 , EndNestedFraction floor left parenthesis, StartNestedFraction, "x" NestedOver 2 pi , EndNestedFraction , right parenthesis , right parenthesis , EndFractionfx=1cosx+2π5floorx2π
12
Now turn on this graph to see the whole thing:
13
運算式 14: "r" equals "f" left parenthesis, theta minus "a" , right parenthesis left brace, StartAbsoluteValue, "f" left parenthesis, theta minus "a" , right parenthesis , EndAbsoluteValue less than sec left parenthesis, StartFraction, 2 pi Over 5 , EndFraction , right parenthesis , right bracer=fθ−afθ−a<sec2π5
