To change the shape of the triangle, move points A, B, and C. [br]To determine the height, move the solid perpendicular line to pass through the vertex opposite the base. [br]Hide/Show the ruler by pressing the ruler button.[br]Change the base by pressing the corresponding base button. [br]Once the height is determined, the perpendicular line will no longer move. You must change the base to another base, and back again.