Question 1071269
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<pre>
Then  sin(x) = {{{sqrt(1 - cos^2(x))}}} = {{{(1 - (-4/5)^2)}}} = {{{sqrt(1 - 16/25)}}} = {{{sqrt((25-16)/25)}}} = {{{sqrt(9/25)}}} = {{{3/5}}}.

The sign at sqrt is "+" since sine is positive in QII.


tan = sin/cos,

csc = 1/sin,

cot = cos/sin,

sec = 1/cos.
</pre>

For many other similar solved problems see the lessons

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/Trigonometry-basics/Calculating-trigonometric-functions-of-angles.lesson>Calculating trigonometric functions of angles</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/Trigonometry-basics/Selected-problems-from-the-archive-on-calculating-trig-functions-of-angles.lesson>Advanced problems on calculating trigonometric functions of angles</A>
in this site.


They are the part of the online textbook 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson>ALGEBRA-II - YOUR ONLINE TEXTBOOK</A>.

under the topic "<U>Trigonometry: Solved problems</U>".