Complementary Angles Calculator
Easily calculate complementary angles or check if two angles are complementary with our complementary angles calculator.
Complementary angle55°35° + 55° = 90°
In radians0.95993109
Known angle in radians0.61086524
Type of the known angleacute
The rule
the two angles add to 90°
Degrees and radians
A full turn is 360° or 2π radians, so:
radians = degrees × π/180 and degrees = radians × 180/π
Degrees are convenient because 360 divides so many ways. Radians are the natural choice in mathematics because arc length becomes simply rθ and the calculus of sine and cosine comes out clean — derivatives pick up stray factors of π/180 in degrees.
Names worth knowing
- Acute — under 90°. Right — exactly 90°. Obtuse — between 90° and 180°.
- Straight — 180°. Reflex — over 180°.
- Complementary pairs add to 90°; supplementary pairs add to 180°.