Thread: radian to degree value problem?

No, you need to do 45 * pi / 180, and then feed that value into sin. There is no (reasonable) way to convert a sin-value from radians to degrees or the other way around, after you have called sin. You need to convert the degrees to radians before calling sin.

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Mats

A "macro" I frequently use for this very thing (it's not a real macro):

Code:

#define degrees 0.0174532925199432958 // to the limit of a double plus a bit extra

Just multiply by this value to convert degrees to radians. For the inverse, you could divide by this value or use this "macro" (it's not a real one):

Code:

#define radians 57.295779513082321 // to the limits of a double plus a bit extra

Using them is done this way:

Code:

TestValue = sin(30.0*degrees); // you should get exactly 0.5
TestValueInverse = asin(TestValue)*radians; // you should get 30 back
TestValueInverse2 = asin(TestValue)/degrees; // the alternative, but less clear method

I do this a lot for calculating slopes in my game. It speeds things up and makes it easy to read as well. Hopefully this will help.

Edit: 30.0 in example usage, not 30 (the latter would be for an int, not a double).

I mainly meant that it's faster to type it. What use is there in using a constant instead?

Code:

const double degrees = 0.0174532925199432958;
const double radians = 57.295779513082321;
...

TestValue = sin(30.0*degrees);
...

For the int/double thing, the program would (I think) have to convert the int to a double, which is a bit CPU intensive compared to just using an all-out double as is.

Originally Posted by ulillillia

I mainly meant that it's faster to type it. What use is there in using a constant instead?

Code:

const double degrees = 0.0174532925199432958;
const double radians = 57.295779513082321;
...

TestValue = sin(30.0*degrees);
...

For the int/double thing, the program would (I think) have to convert the int to a double, which is a bit CPU intensive compared to just using an all-out double as is.

Yes, but conversion to double will happen at compile-time for constants, so it's no cost at the runtime phase of the code. [At least for decent compilers, which includes the two most popular here: gcc and Microsofts C/C++]

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Mats