A right angle was a type of angle that measured 90°. A triangle with a right angle in it was called a right triangle.
In 2257, Christopher Pike told the computer to rotate an image of signals provided by Starfleet by 90° counterclockwise and found it nearly matched a drawing done by Spock. (DIS: "New Eden")
In 2364, Wesley Crusher added to Geordi La Forge's explanation of starship headings to Lore, saying that saying "mark" "separates it from another full three hundred and sixty degree circle this way on a right angle to this one." (TNG: "Datalore")
(DS9: "The Begotten")
Brad Boimler told Taylor he had to reach for power cylinders at a 90° angle, not 80. (LD: "In the Cradle of Vexilon")
(DIS: "Anomaly")