#include <stdio.h>

float thirdAngle(float angleA, float angleB){
	return angleA + angleB;
}

int main(int argc, const char * argv[]){
	float angleA = 30.0;
	float angleB = 60.0;
	float angleC = thirdAngle(angleA, angleB);

	printf("The third angle is %.2f\n", angleC);
	return 0;
}

The third angle is 90.00