How do you find the exact value of Sec(Arctan (1/2))sec(arctan(12))?

1 Answer
Apr 27, 2016

2/sqrt 525

Explanation:

Let a = arc tan (1/2). Then tan a = 1/2. So, sec a = 2/sqrt 5tana=12.So,seca=25, using sec a = +-sqrt ( 1 + tan^2a)=+-sqrt ( 1+ 1/4) = +-2/sqrt 5seca=±1+tan2a=±1+14=±25. Here, tan a is positive. So, sec a is positive and = 2/sqrt 5=25

Now, sec(arc tan (1/2))=sec(arc sec(2/sqrt 5))=2/sqrt5sec(arctan(12))=sec(arcsec(25))=25