计算：sec 67.5度，等于多少？

Question

求67.5度的正割值

Answer 1

sin45°=1-2(sin22.5°)^2
√2/2 =1-2(sin22.5°)^2
sin22.5°
=√[(2-√2)/4]
sec67.5°
=1/cos67.5°
=1/sin22.5°
=2/√(2-√2)本回答被提问者采纳

Answer 2

sin22.5°=sin(45°/2)=√[(1-cos45°)/2]=[√(4-√2)]/2
sec67.5°=1/cos67.5°=1/sin22.5°=[√(4+√2)]/7

Answer 3

是余割
sec 67.5° = 1/cos67.5° = 1/√[(1+cos135°)/2] = 1/√(1-√2/2)/2] = 2/√(2-√2)