sec 2 ( 30 ∘ ) − cos ( 45 ∘ ) = 1 2 − 2 2 = 1 − 2 2 {\displaystyle \sec 2(30^{\circ })-\cos(45^{\circ })={\frac {1}{2}}-{\frac {\sqrt {2}}{2}}={\frac {1-{\sqrt {2}}}{2}}}
