Arccos of √2/2

Arcsin, Arccos, Arctan, Arccot
Function
x

What is arccos(√2/2)?

Answer

arccos(√2/2) =
45° = π/4

Range: arccos x is an angle from 0° to 180°, so the answer is unique.

arccos(√2/2) is the angle α in [0°, 180°] with cos α = √2/2.

cos 45° = √2/2 ✓

xyOP

α = arccos(√2/2) = 45°

P(cos 45°, sin 45°) = (√2/2, √2/2)

P lies on the line x = √2/2 in the upper half of the circle, where sin α ≥ 0; highlighted: cos α = √2/2.

All four inverse functions of √2/2
FunctionDegreesRadians
arcsin(√2/2)45°π/4
arccos(√2/2)45°π/4
arctan(√2/2)≈ 35.2644°≈ 0.6155
arccot(√2/2)≈ 54.7356°≈ 0.9553

See Also

FAQ

What is arccos(√2/2)?

arccos(√2/2) = 45° = π/4

How to find arccos(√2/2) from a table of cosines?

Look in the table for the angle α in [0°, 180°] with cos α = √2/2: it is 45°, or π/4 in radians.

Why does a calculator show 0.7854 for arccos(√2/2)?

The calculator is in radian mode (RAD) and gives the angle in radians: arccos(√2/2) = π/4 ≈ 0.7854 rad. In degrees (DEG) it is 45°.