What is the syntax for ACOT in Excel?

The syntax for ACOT is: =ACOT(number)

What is ACOT in Excel and how does it work?

ACOT returns the arccotangent (inverse cotangent) of a number in radians. The syntax is =ACOT(number). For example, =ACOT(1) returns π/4 (0.785 radians). ACOT is the inverse of COT, so COT(ACOT(x)) = x. The result is always between 0 and π.

What is the difference between ACOT and ATAN?

ACOT and ATAN are related: ACOT(x) = ATAN(1/x) - π/2 for x 0. ACOT returns values from 0 to π, while ATAN returns values from -π/2 to π/2. Both return radians. Use ACOT when you have cotangent values, ATAN for tangent values.

How do I convert ACOT result to degrees?

ACOT returns radians. To convert to degrees, multiply by 180/PI: =ACOT(number) * 180/PI(). For example, =ACOT(1) * 180/PI() returns 45 degrees. Alternatively, use DEGREES: =DEGREES(ACOT(number)).

Why is ACOT useful in trigonometry?

ACOT is useful when you know the cotangent of an angle and need to find the angle itself. It's commonly used in engineering calculations, navigation, and physics problems involving right triangles. ACOT helps solve equations where cotangent values are known but angles need to be determined.

Can ACOT handle negative numbers?

Yes, ACOT accepts any real number (positive, negative, or zero). For negative inputs, ACOT returns values between π/2 and π. For example, =ACOT(-1) returns approximately 2.356 (3π/4 radians). The result is always in the range [0, π].

Math & Trig

ACOT Function in Excel

Returns the arccotangent of a number in radians.

Syntax

=ACOT(number)

Arguments

number (required): Cotangent value

Examples

=ACOT(1) - Arccotangent of 1 - Result: 0.785 (π/4)

ACOT in reporting workflows

Use absolute references when copying formulas across rows.
For conditional totals see [SUMIF](/functions/sumif/) and [SUMIFS](/functions/sumifs/).
Filtered lists may need [SUBTOTAL](/functions/subtotal/) instead of SUM on visible cells only.

Common errors

Result between 0 and PI

Use cases

Trigonometry
Angle calculations
Engineering

Frequently asked questions

What is ACOT in Excel and how does it work? ACOT returns the arccotangent (inverse cotangent) of a number in radians. The syntax is =ACOT(number). For example, =ACOT(1) returns π/4 (0.785 radians). ACOT is the inverse of COT, so COT(ACOT(x)) = x. The result is always between 0 and π.
What is the difference between ACOT and ATAN? ACOT and ATAN are related: ACOT(x) = ATAN(1/x) - π/2 for x < 0, and ACOT(x) = ATAN(1/x) for x > 0. ACOT returns values from 0 to π, while ATAN returns values from -π/2 to π/2. Both return radians. Use ACOT when you have cotangent values, ATAN for tangent values.
How do I convert ACOT result to degrees? ACOT returns radians. To convert to degrees, multiply by 180/PI: =ACOT(number) * 180/PI(). For example, =ACOT(1) * 180/PI() returns 45 degrees. Alternatively, use DEGREES: =DEGREES(ACOT(number)).
Why is ACOT useful in trigonometry? ACOT is useful when you know the cotangent of an angle and need to find the angle itself. It's commonly used in engineering calculations, navigation, and physics problems involving right triangles. ACOT helps solve equations where cotangent values are known but angles need to be determined.
Can ACOT handle negative numbers? Yes, ACOT accepts any real number (positive, negative, or zero). For negative inputs, ACOT returns values between π/2 and π. For example, =ACOT(-1) returns approximately 2.356 (3π/4 radians). The result is always in the range [0, π].

Editorial review

Reviewed by Excel.Directory Editorial Team. Updated May 2026.