Mathematics
OpenStudy (anonymous):

When doing trig, I came across this puzzler: http://mathb.in/433 Why is this so? W|A confirms: http://bit.ly/JmEk6p

OpenStudy (accessdenied):

Secant is the reciprocal function of cosine. So, if you take the secant of both sides, you get x = sec(cos^-1(1/x)) Since sec = 1/cos; x = 1/cos(cos^-1(1/x)) = 1/(1/x) = x

OpenStudy (accessdenied):

That's kind of a non-rigorous way of showing it, I guess. :P

OpenStudy (binary3i):

$y=cosx$ $x=\cos^{-1}y$ $1/y = 1/cosx = secx$ $\sec^{-1} 1/y = x$ so there comes your ans wer

OpenStudy (kropot72):

|dw:1338092907462:dw| In the triangle $\sec y=\frac{x}{1}$ $\cos y=\frac{1}{x}$