Question 1202951
<br>
Because the inverse sine is positive for both angles, they are both in quadrant I.<br>
Draw a right triangle in standard position with a sine (opposite over hypotenuse) of 2/5 and use {{{sin^2(x)+cos^2(x)=1}}} to determine that the cosine of the angle is sqrt(21)/5, which is the sine of the other angle in the given expression.<br>
In a right triangle, the sine of one acute angle is the cosine of the other, so the two angles in the given expression are the two angles in a right triangle.  So the sum of the two angles is 90 degrees.<br>
ANSWER: 90 degrees<br>