I try to write code for that calculation angles from lengths of triangle. formula is cos(a)=b^2+c^2-a^2/2bc. (Triangle is here)
angle1 = acosf((powf(length2,2) + powf(length3,2) - powf(length1,2)) / 2 * length2 * length3)* 180 / 3.14153;
angle2 = acosf((powf(length1,2) + powf(length3,2) - powf(length2,2)) / 2 * length1 * length3)* 180 / 3.14153;
angle3 = 180 - (angle2 + angle1);
Everything is float. When entered 5-4-3 inputs outcome this.
angle one is 90.0018
angle two is nan
angle three is nan
changing order doesn't matter, only gives output for 5.
You are doing:
angle1 = acosf((powf(length2,2) + powf(length3,2) - powf(length1,2)) / 2 * length2 * length3)* 180 / 3.14153;
You should be doing:
angle1 = acosf((powf(length2,2) + powf(length3,2) - powf(length1,2)) / (2 * length2 * length3))* 180 / 3.14153;
Explanation: The problem is caused by the following formula, which is in fact badly written:
cos(a)=b^2+c^2-a^2/2bc
// This, obviously, is wrong because
// you need to group the firt three terms together.
// Next to that, everybody understands that the last "b" and "c" are divisors,
// yet it would be better to write it as:
cos(a)=(b^2+c^2-a^2)/(2bc)
The brackets, I added in the code, are similar to the replacement of /2bc by /(2bc).