diff -r 56cd8111b7f7 -r 41300fa6a67c src/corelib/tools/qline.cpp
--- a/src/corelib/tools/qline.cpp	Tue Jan 26 12:42:25 2010 +0200
+++ b/src/corelib/tools/qline.cpp	Tue Feb 02 00:43:10 2010 +0200
@@ -574,7 +574,7 @@
     const qreal dx = pt2.x() - pt1.x();
     const qreal dy = pt2.y() - pt1.y();
 
-    const qreal theta = atan2(-dy, dx) * 360.0 / M_2PI;
+    const qreal theta = qAtan2(-dy, dx) * 360.0 / M_2PI;
 
     const qreal theta_normalized = theta < 0 ? theta + 360 : theta;
 
@@ -814,7 +814,7 @@
     qreal cos_line = (dx()*l.dx() + dy()*l.dy()) / (length()*l.length());
     qreal rad = 0;
     // only accept cos_line in the range [-1,1], if it is outside, use 0 (we return 0 rather than PI for those cases)
-    if (cos_line >= -1.0 && cos_line <= 1.0) rad = acos( cos_line );
+    if (cos_line >= -1.0 && cos_line <= 1.0) rad = qAcos( cos_line );
     return rad * 360 / M_2PI;
 }