If in a triangle, one angle is a right angle, then no other angle can be an obtuse angle.
For e.g in Δ ABC, if ∠B is right angle, then
m∠A + m∠B + m∠C=180
∴m∠A + 90 + m∠C=180
∴m∠A + m∠C=90
Thus the sum of remaining two angles is 90° and so none of them could be obtuse or even a right angle.