You can easily draw basic shapes like these using Path
Triangle
<s:Path data="M 0 0 L 5 10 L 10 0 Z">
<s:stroke>
<s:SolidColorStroke color="0x000000"/>
</s:stroke>
</s:Path>
Trapezoid
<s:Path data="M 0 0 L 10 0 L 7 5 L 3 5 Z">
<s:stroke>
<s:SolidColorStroke color="0x000000"/>
</s:stroke>
</s:Path>
Legend
- M: move to (don't draw)
- L: draw line to
- Z: close the shape
For more info read the docs