A 99° angle is an obtuse angle: wider than a right angle (90°) but less than a straight line (180°). Its supplement is 81°, so a 99° angle and an 81° angle side by side make a straight line.
99° is 11/40 of a full circle, or 11π/20 radians. If you face north and turn 99° clockwise, you end up facing between E and ESE (closest to east (E)).
99° angle facts
| Angle type | Obtuse angle (between 90° and 180°) |
|---|---|
| Supplement (adds to 180°) | 81° |
| Explement (adds to 360°) | 261° |
| Radians | 11π/20 ≈ 1.727876 |
| Gradians | 110 grad |
| Fraction of a turn | 11/40 (27.5%) |
| Degrees, minutes, seconds | 99° 0′ 0″ |
| Compass bearing | between E and ESE (closest to east (E)) |
Trigonometric values of 99°
| Function | Value |
|---|---|
| sin 99° | 0.987688 |
| cos 99° | −0.156434 |
| tan 99° | −6.313752 |
99° on a protractor
How to draw a 99° angle with a protractor
- Draw a straight line with a ruler. This is the first arm; mark the vertex at one end.
- Place the center mark of the protractor exactly on the vertex and line up the 0° baseline with your line.
- Find 99° on the row of numbers that reads 0° on your line (protractors have two rows running in opposite directions) and make a small dot at the edge.
- Remove the protractor and draw a line from the vertex through the dot. Mark the angle with an arc and label it 99°.
Drawing it a 99° angle without a protractor (rise and run method)
- 99° = 180° − 81°. Draw a straight line, pick a vertex on it, and build an 81° angle on one side as follows; the angle on the other side of the new line is 99°.
- Draw a straight baseline and measure 1.58 inches (about 1 9/16″) along it from the vertex.
- At that mark, draw a line straight up at 90° and measure exactly 10 inches up it.
- Join the top mark to the vertex. The angle at the vertex is 81°, because tan 81° ≈ 6.3138.
Where you see 99° angles
- The Earth turns 99° on its axis in about 6 h 36 min.
- Obtuse angles like 99° appear in reclining chair backs, open laptop screens, fan blades, and the corners of many-sided polygons.
Related angles
99° angle FAQ
What type of angle is 99°?
A 99° angle is an obtuse angle, because it is between 90° and 180°.
What is the supplement of 99°?
The supplement of 99° is 81°, because 99° + 81° = 180°. A 99° angle has no complement, because it is already larger than 90°.
How many radians is 99 degrees?
99° = 11π/20 radians ≈ 1.7279 rad. To convert degrees to radians, multiply by π/180: 99 × π/180 = 11π/20.
How do I measure a 99° angle on my screen?
Open the online protractor with 99° preset, or type 99 into its "Type an angle" box. You can then drag the arms onto your own lines to compare.
