Isosceles Triangle Investigation

  • Isosceles Triangle Investigation

    Grade: High School

    Isosceles ΔABC is constructed so that AB = AC = 5. Use this tool to investigate the relationship between the area of the triangle and the length of its base (BC).

    Activity

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    Instructions

    • Drag point C to change the base and height of isosceles ΔABC.
    • The length of the base and the area of the triangle will be recalculated as the triangle is modified; additionally, a trace will be created by the movement of point L, which shows a graph of the area as a function of BC.
    • Note that the triangle disappears if points B and C overlap (that is, if BC = 0). Similarly, the triangle will disappear if BC > 10, as this is a violation of the Triangle Inequality.

    Exploration

    When does the area of triangle ABC reach its maximum? What is the relationship between the base and and height?

    Objectives and Standards

    NCTM Standards and Expectations
    • Geometry / Measurement
    • Understand that by similarity, side ratios in right triangles are properties of the angles in the triangle, leading to definitions of trigonometric ratios for acute angles.
    • High School (9-12)
    • Geometry