refactoring: arcTangent function test, rename

src/test/test_funktionen.c

@@ -167,7 +167,7 @@ void test_arcCosine_for_0_5(void) {
     // Add more test cases for different inputs and expected outputs
 }
 
-void test_arcTangent(void) {
+void test_arcTangent_for_1_0(void) {
     float result = arcTangent(1.0);
     TEST_ASSERT_EQUAL_FLOAT(0.785398, result);
     // Add more test cases for different inputs and expected outputs