解: tan50°
=tan(45°+5°)
=(tan45°+tan5°)/(1-tan45°Xtan5°)
=(1+tan5°)/(1-1Xtan5°)
=(1+tan5°)/(1-tan5°)
=(1+tan5°)²/(1-tan²5°)
≈(1+tan5°)²
≈1.19
角度计算
用tan(a/2)表示角a的三角函数(其中tan^2(a/2)=tan(a/2)*tan(a/2))
sinα=(2tan(a/2))/(1+tan^2(a/2))
cosα=(1-tan^2(a/2))/(1+tan^2(a/2))
tanα=(2tan(a/2))/(1-tan^2(a/2))
cotα=(1-tan^2(a/2))/(2tan(a/2))
secα=(1+tan^2(a/2))/(1-tan^2(a/2))
cscα=(1+tan^2(a/2))/(2tan(a/2))