# Find the value of 'trig of inverse trig' questions

• Apr 9th 2010, 05:32 PM
sydewayzlocc
Find the value of 'trig of inverse trig' questions
Evaluate each expression

tan(arccos(http://www.webassign.net/wastatic/watex/img/sqrt1a.gif2/2))

cos(arcsin(5/13))
• Apr 9th 2010, 05:37 PM
harish21
Quote:

Originally Posted by sydewayzlocc
Evaluate each expression

tan(arccos(http://www.webassign.net/wastatic/watex/img/sqrt1a.gif2/2))

cos(arcsin(5/13))

$tan(arccos(\frac{\sqrt2}{2})) = tan(\frac{\pi}{4}) = 1$

what you need to notice: $cos(\frac{\pi}{4}) = \frac{\sqrt{2}}{2}$

what you need to remember: $arccos(cos(x)) = cos^{-1}(cos(x)) = x$

$\therefore arccos(cos(\frac{\pi}{4})) = arccos(\frac{\sqrt{2}}{2})$

so, $\frac{\pi}{4} = arccos(\frac{\sqrt{2}}{2})$

Try the second one.