an angle of 90 degrees
The interior angles of a square are right angles.
Carriers are to be requested to stick to the regulations which set the approach and takeoff angles at no less than 45 degrees. (Certificate of Proficiency in English; C2; Polish)
The picture was hanging at an angle, so I straightened it.
I needed to tilt the unit at an angle for it to work. (International English Language Testing System; C1; Others)
This is the same building photographed from different angles.
It is possible to see all the paintings from different angles. You can also zoom in and out. (Certificate in Advanced English; C1; Swedish)
Try looking at the problem from another angle.
To be a child is to see the world from a different angle. (Certificate in Advanced English; C1; Greek)