Use the `Math.Atan`

,
`Math.Acos`

, or `Math.Asin`

static
methods of the `Math`

class. The following code
calculates the angle `theta`

and returns the value
in *radian* measure:

double theta = Math.Atan(OppositeSide / AdjacentSide); theta = Math.Acos(AdjacentSide / Hypotenuse); theta = Math.Asin(OppositeSide / Hypotenuse);

To get the angle in degrees, use the following code:

double theta = Math.Atan(oppositeSide / adjacentSide) * (180 / Math.PI); theta = Math.Acos(adjacentSide / hypotenuse) * (180 / Math.PI); theta = Math.Asin(oppositeSide / hypotenuse) * (180 / Math.PI);

where `theta`

is the known angle value, the
`oppositeSide`

is equal to the length of the side
*opposite* to the angle, and
`adjacentSide`

is equal to the length of the side
*adjacent* to the angle. The
`hypotenuse`

is the
length of the *hypotenuse* of the triangle. See
Figure 1-1 in Recipe 1.14
for a graphical representation of these sides of a right triangle.

In some cases, we need to determine an angle of a right triangle when
only the lengths of two sides are known. The three trigonometric
functions
arcsine, arccosine, and arctangent allow
us to find any angle of a right triangle, given this information. The
static methods `Math.Atan`

,
`Math.Acos`

, and `Math.Asin`

on the
`Math`

class provide the functionality to implement
these trigonometric operations.

See Recipe 1.14; see the “Math Class” topic in the MSDN documentation.

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