This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
1) You really don't want to place a JComponent on a Frame, trust me. Put it in a JFrame.
2) To set the triangle as equilateral, calculate the height vs base of an equilateral triangle (any basic geometry text will tell you, something about sqrt(3)/2), and use these numbers to set your preferred size of the jcomponent.