角度轉換~~~

1)
cot(90-x) = tanx
sec(90-x) = cscx
csc(90-x) = secx

as all functions would have +ve for angle between 0 and 90.

2)
cot(270-x) = tanx
sec(270-x) = -cscx
csc(270-x) = -secx

as cot would have +ve for angle between 180 and 270.

3)
cot(90+x) = -tanx
sec(90+x) = -cscx
csc(90+x) = secx

as csc would have +ve for angle between 90 and 180.

4)
cot(270+x) = -tanx
sec(270+x) = cscx
csc(270+x) = -secx

as csc would have +ve for angle between 270 and 360.

5)
a)
cot(x-90) = -tanx
sec(x-90) = cscx
csc(x-90) = -secx

b)
cot(x-270) = -tanx
sec(x-270) = cscx
csc(x-270) = -secx

the reason is that sec(-x) = secx, but cot(-x) = -cotx and csc(-x) = -cscx for any x.

There is no difference for x+a or a+x for a = 90 or 270.