Find in radian measure of arctan(1/2)+arctan(1/3)?

1 Answer
May 14, 2018

π4.

Explanation:

Recall that, arctanx+arctany=arctan(x+y1xy),0<xy<1.

Accordingly, since, 0<1213=16<1,

arctan(12)+arctan(13)=arctan(12+1311213),

=arctan(5656),

=arctan1,

=π4, is the desired value!