Công cụ tính toán góc lượng giác (độ dốc)

In product design, inclined angles (slopes) are quite common. This tool lets you easily determine the inclination angle from two sides of a right triangle.

When a and b are known

Formula 1 diagram
θ = - rad
= - Deg
= -
Side c = -
【Calculation formula】:

θ = TAN-1(b/a)×180/π = Deg
c = √(a2 + b2) =

When a and c are known

Formula 2 diagram
θ = - rad
= - Deg
= -
Side b = -
【Calculation formula】:

θ = COS-1(a/c)×180/π = Deg
b = √(c2 - a2) =

When b and c are known

Formula 3 diagram
θ = - rad
= - Deg
= -
Side a = -
【Calculation formula】:

θ = SIN-1(b/c)×180/π = Deg
a = √(c2 - b2) =

Theory: calculating inclination angles

The inclination angle can be calculated if the lengths of two sides of a right triangle are known.

The angle θ calculated by this formula is in radians (rad), using the circular arc system.

There are two angle representation systems: radian and degrees–minutes–seconds. The radian system uses rad; the DMS system uses degrees, where 1°=60 minutes.

What is the radian system?
The radian system expresses the angle where the central angle subtending an arc equal to the radius is 1 radian. (1 rad ≈ 57.3°)

What is the sexagesimal degree system?
The degree system divides a full circle into 360 equal parts. Radians are commonly used in engineering and math, so knowing how to convert between them is essential.

Relationship between radians and degrees
Degrees = Radians × 180 ÷ π
1 rad = 57,3°
1° = π / 180 rad

Explanation of angles (degrees · minutes · seconds)
1 minute (1′) = 1/60 of 1 degree. E.g. 30 minutes = 0.5°. Symbol: single prime (').
1 second (1″) = 1/3600 of 1 degree. Symbol: double prime (").

When representing angles smaller than 1 degree in CAD drawings, the DMS notation is sometimes used.

DMS angle table

Explanation of side length calculations
For a right triangle with legs a, b and hypotenuse c, the Pythagorean theorem gives:

Pythagorean theorem

Therefore, knowing any two sides is sufficient to find the third. E.g. when b and c are known, a is:

Formula for side a