Question 1058467
<pre><b><font size=4>
Memorize the 6 trig ratios for the negative angles:
(only the cosine and secant don't change the sign)

sin(-x) = -sin(x)
cos(-x) = cos(x)
tan(-x) = -tan(x)
sec(-x) = sec(x)
csc(-x) = -csc(x)
cot(-x) = -cot(x)

{{{ cos(-x)cot(x)sin(-x) }}}{{{""=""}}}

{{{ cos(x)cot(x)(-sin(x)^"") }}}{{{""=""}}}

{{{ -cos(x)cot(x)sin(x) }}}{{{""=""}}}

Use the identity {{{cot(theta)=cos(theta)/sin(theta)}}}

{{{ -cos(x)*expr(cos(x)/sin(x))sin(x) }}}{{{""=""}}}

{{{ -cos(x)*expr(cos(x)/cross(sin(x)))cross(sin(x)) }}}{{{""=""}}}

{{{ -cos(x)cos(x) }}}{{{""=""}}}

{{{ -cos^2(x) }}}

Edwin</pre></b></font>