How do you evaluate sec^-1(sec((7pi)/10))sec1(sec(7π10))?

1 Answer
Mar 26, 2017

(7pi)/107π10

Explanation:

sec^(-1)xsec1x is defined for xin(R-]-1,1[)rarr([0,pi]-{pi/2})(R]1,1[)([0,π]{π2}).
sec^(-1)secx= xsec1secx=x if and only if xin([0,pi]-{pi/2})([0,π]{π2}).
in your question, since (7pi)/10in([0,pi]-{pi/2})7π10([0,π]{π2})
so, sec^(-1)sec((7pi)/10)=(7pi)/10sec1sec(7π10)=7π10