c++ - How to draw a line at angle in QT? -

i have co-ordinate , angle. want draw line co-ordinate upto length specified angle. how can achieve this?? can give idea?

arthur's way of computing angle correct, actually, qt provides built-in methods of drawing lines @ specific angles, in particular functions of qlinef class in qlinef header:

#include <qlinef>  void angledemo::paintevent(qpaintevent *) {   qpainter painter(this);    painter.setpen(qpen(qt::black,1));    /* create line object: */   qlinef angleline;    /* set origin: */   angleline.setp1(qpointf(80,80));    /* set angle , length: */   angleline.setangle(45);   angleline.setlength(50);    /* draw line: */   painter.drawline(angleline); } 

from online documentation of setangle() function:

sets angle of line given angle (in degrees). change position of second point of line such line has given angle.

positive values angles mean counter-clockwise while negative values mean clockwise direction.

zero degrees @ 3 o'clock position.

this function introduced in qt 4.4.