It would seem that could be easier?
However, for beginners it can be a real problem as the "triangle" figure is not standard tools Adobe Illustrator.
method one. Select the Pen tool (press [P]) andclick in three places for the working area of the triangular shape and the fourth time to the first point to close the circuit. Also, you can close the loop by selecting three points and then pressing the key combination [Ctrl + J].
method two. Select the Line Segment (key ) and the tooldraw three straight lines so that the end of the previous line coincided with the beginning of the next (the end of the third line should coincide with the beginning of the first). Select the resulting line and press [Ctrl + J], to close the loop.
The third way. Select the Rectangle (key [M]) and tooldraw a rectangle. Next, select the Delete Anchor Point tool (press [-]) and click one of the corner points of the rectangle to remove it.
method fourth. Select the Polygon tool from the same menu,where there is a Rectangle. Click on the workspace and hold down the left mouse button, you can press the keyboard up and down arrows to adjust the number of corners of the polygon.
method fifth. Select Star Tool from the same menu, whereis Polygon. Click on the workspace and hold down the left mouse button, you can press the keyboard up and down arrows to adjust the number of all the stars.