cos(45°) = 0.70710678, exactly √2/2.
cos(45°) = 0.70710678, exactly √2/2. The angle 45° equals π/4 radians (45 × π/180).
Exact form: √2/2. Decimal: 0.70710678 (rounded to 8 places).
45° lies quadrant I. 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 π/4 instead of 45.
| sin 45° | = 0.70710678 |
| cos 45° | = 0.70710678 |
| tan 45° | = 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(45°) = 0.70710678, exactly √2/2.
45° = π/4 radians, so cos(45°) = cos(π/4) = 0.70710678.
It is most likely set to radians. Switch to degree (DEG) mode before entering the angle.
Positive.
Yes. Use the calculator on this page, or open the full free Scientific Calculator with memory, history and keyboard support.