Question 989314
<pre>
The six trig ratios for {{{pi/4}}} are

{{{sin(pi/4)}}}{{{""=""}}}{{{sqrt(2)/2}}}
{{{cos(pi/4)}}}{{{""=""}}}{{{sqrt(2)/2}}}
{{{tan(pi/4)}}}{{{""=""}}}{{{1}}}
{{{sec(pi/4)}}}{{{""=""}}}{{{sqrt(2)}}}
{{{csc(pi/4)}}}{{{""=""}}}{{{sqrt(2)}}}
{{{cot(pi/4)}}}{{{""=""}}}{{{1}}}

{{{5pi/4}}} is in QIII because:

{{{pi}}}{{{""<""}}}{{{1.25pi}}}{{{""=""}}}{{{5pi/4}}}{{{""<""}}}{{{1.5pi}}}{{{""=""}}}{{{3pi/2}}}

In QIII, only the tangent and cotangent are positive, others negative, so:

{{{sin(5pi/4)}}}{{{""=""}}}{{{-sqrt(2)/2}}}
{{{cos(5pi/4)}}}{{{""=""}}}{{{-sqrt(2)/2}}}
{{{tan(5pi/4)}}}{{{""=""}}}{{{1}}}
{{{sec(5pi/4)}}}{{{""=""}}}{{{-sqrt(2)}}}
{{{csc(5pi/4)}}}{{{""=""}}}{{{-sqrt(2)}}}
{{{cot(5pi/4)}}}{{{""=""}}}{{{1}}}

Edwin</pre>