A 170° angle is obtuse because it is greater than 90° and less than 180°. Its supplement is 10°, so a 170° angle and a 10° angle side by side make a straight line.
170° is 17/36 of a full circle, or 17π/18 radians. If you face north and turn 170° clockwise, you end up facing between SSE and S (closest to south (S)).
170° angle facts
| Angle type | Obtuse angle (between 90° and 180°) |
|---|---|
| Supplement (adds to 180°) | 10° |
| Explement (adds to 360°) | 190° |
| Radians | 17π/18 ≈ 2.96706 |
| Gradians | 188.8889 grad |
| Fraction of a turn | 17/36 (47.22%) |
| Degrees, minutes, seconds | 170° 0′ 0″ |
| Compass bearing | between SSE and S (closest to south (S)) |
Trigonometric values of 170°
| Function | Value |
|---|---|
| sin 170° | 0.173648 |
| cos 170° | −0.984808 |
| tan 170° | −0.176327 |
170° on a protractor
How to draw a 170° 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 170° 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 170°.
Drawing it a 170° angle without a protractor (rise and run method)
- 170° = 180° − 10°. Draw a straight line, pick a vertex on it, and build a 10° angle on one side as follows; the angle on the other side of the new line is 170°.
- Draw a straight baseline and measure exactly 10 inches along it from the vertex.
- At the 10-inch mark, draw a short line straight up at 90° (use a carpenter's square or the corner of a sheet of paper).
- Measure 1.76 inches (about 1 3/4″) up that line and make a mark.
- Join the mark to the vertex. The angle at the vertex is 10°, because tan 10° ≈ 0.1763.
Where you see 170° angles
- Each interior corner of a regular 36-sided polygon measures 170°.
- The Earth turns 170° on its axis in about 11 h 20 min.
- Obtuse angles like 170° appear in reclining chair backs, open laptop screens, fan blades, and the corners of many-sided polygons.
Related angles
170° angle FAQ
What type of angle is 170°?
A 170° angle is an obtuse angle, because it is between 90° and 180°.
What is the supplement of 170°?
The supplement of 170° is 10°, because 170° + 10° = 180°. A 170° angle has no complement, because it is already larger than 90°.
How many radians is 170 degrees?
170° = 17π/18 radians ≈ 2.9671 rad. To convert degrees to radians, multiply by π/180: 170 × π/180 = 17π/18.
How do I measure a 170° angle on my screen?
Open the online protractor with 170° preset, or type 170 into its "Type an angle" box. You can then drag the arms onto your own lines to compare.
