2 s e c ( ∘ π 4 ) − cos ( 45 ∘ ) = 1 2 − 2 2 = 1 − 2 2 {\displaystyle \ 2sec({\circ }{\frac {\pi }{4}})-\cos(45^{\circ })={\frac {1}{2}}-{\frac {\sqrt {2}}{2}}={\frac {1-{\sqrt {2}}}{2}}}
