Question 965344
<pre>
That's not a special angle, so you'll have to use a 
calculator.

If you have a TI graphing calculator,

Make sure it's in RADIAN mode:

Press MODE
Scroll down to the third line RADIAN DEGREE.
Make sure RADIAN is highlighted.

Press 2ND then MODE to get back to the main screen.

Press CLEAR

Press 2ND then TAN, you'll see tan<sup>-1</sup>(

Type 3/7) after that so you see  tan<sup>-1</sup>(3/7)

Press ENTER

Read   .4048917863

Edwin</pre>