cos(225°) = -0.70710678, exactly −√2/2.
cos(225°) = -0.70710678, exactly −√2/2. The angle 225° equals 5π/4 radians (225 × π/180).
Exact form: −√2/2. Decimal: -0.70710678 (rounded to 8 places).
225° lies quadrant III. Remember that cosine is positive in quadrants I and IV, and negative in the others, which decides the sign of the answer.
If you get a different number, the calculator is probably in RAD mode. In radians you would enter 5π/4 instead of 225.
| sin 225° | = -0.70710678 |
| cos 225° | = -0.70710678 |
| tan 225° | = 1 |
| Angle | Radians | Cos |
|---|---|---|
| 0° | 0 | 1 |
| 30° | π/6 | 0.866025 |
| 45° | π/4 | 0.707107 |
| 60° | π/3 | 0.5 |
| 90° | π/2 | 0 |
| 120° | 2π/3 | -0.5 |
| 135° | 3π/4 | -0.707107 |
| 150° | 5π/6 | -0.866025 |
| 180° | π | -1 |
| 270° | 3π/2 | 0 |
| 360° | 2π | 1 |
cos(225°) = -0.70710678, exactly −√2/2.
225° = 5π/4 radians, so cos(225°) = cos(5π/4) = -0.70710678.
It is most likely set to radians. Switch to degree (DEG) mode before entering the angle.
Negative.
Yes. Use the calculator on this page, or open the full free Scientific Calculator with memory, history and keyboard support.