Arccos of 1/5

Arcsin, Arccos, Arctan, Arccot
Function
x

What is arccos(1/5)?

Answer

arccos(1/5) ≈
78.4630° ≈ 1.3694 rad

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

≈ — the value is not a table one; rounded to 4 decimal places.

1/5 = 0.2.

arccos(1/5) is the angle α in [0°, 180°] with cos α = 1/5.

cos 78.4630° ≈ 0.2000

xyOP

α = arccos(1/5) ≈ 78.4630°

P ≈ (0.2, 0.9798)

P lies on the line x = 1/5 in the upper half of the circle, where sin α ≥ 0; highlighted: cos α = 1/5.

All four inverse functions of 1/5
FunctionDegreesRadians
arcsin(1/5)≈ 11.5370°≈ 0.2014
arccos(1/5)≈ 78.4630°≈ 1.3694
arctan(1/5)≈ 11.3099°≈ 0.1974
arccot(1/5)≈ 78.6901°≈ 1.3734

See Also

Recalculate with different values ↑

Arccosine of nearby values

xarccos x
090° = π/2
0.1≈ 84.2608°
0.14≈ 81.9522°
1/5≈ 78.4630°
1/4≈ 75.5225°
0.3≈ 72.5424°
1/3≈ 70.5288°

FAQ

What is arccos(1/5)?

arccos(1/5) ≈ 78.4630° ≈ 1.3694 rad

How to convert arccos(1/5) to radians?

Multiply the angle in degrees by π/180: 78.4630° × π/180 ≈ 1.3694 rad.

Why does a calculator show 1.3694 for arccos(1/5)?

The calculator is in radian mode (RAD) and gives the angle in radians: arccos(1/5) ≈ 1.3694 rad. In degrees (DEG) it is ≈ 78.4630°.

See Also