math.acos

local result = math.acos(
    value
)

Type	Name	Description
`number`	value	Cosine value in the range [-1, 1]

Type	Name	Description
`number`	result	Arc cosine in radians, in the range [0, pi]

Arc cosine of 1 is 0

local result = math.acos(1)

engine.print("info", result) -- 0.0

Arc cosine of 0 is pi/2

local result = math.acos(0)

engine.print("info", result) -- 1.5707963267949

Arc cosine of -1 is pi

local result = math.acos(-1)

engine.print("info", result) -- 3.1415926535898

Arc cosine of 0.5 is 60 degrees

local result = math.deg(math.acos(0.5))

engine.print("info", result) -- 60.0

Compute angle between two normalized vectors

local dot_product = 0.5
local angle_deg = math.deg(math.acos(dot_product))

engine.print("info", angle_deg) -- 60.0

Verify acos and cos are inverses

local angle = math.pi / 3
local result = math.acos(math.cos(angle))

engine.print("info", result) -- 1.0471975511966