Free · Algebra and geometric models

Trapezoid Area and Inclined Legs

Relate trapezoid bases, perpendicular height, side lengths and supplementary interior angles.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

For the worked inputs, Area (A) = 20.

A=(a+b)h/2; h=c sin α=d sin δ

Worked example

Enter these known values and leave the other values blank.

a (base)
8 cm
b (base)
2 cm
h (height)
4 cm
Area (A)
20 cm²

Assumptions and limitations

  • The bases are parallel and height is their perpendicular separation.
  • The longer base is a. Sloping-leg inverses select the principal acute branch; supplementary-angle alternatives require a complete consistent configuration.

Common questions

What must I enter?

Choose the mode when available and enter its independent known quantities. Leave an unknown editable quantity empty to use a supported inverse.

How should I use the result?

Interpret the numbers within the stated mathematical assumptions. Available unit selectors convert quantities; display rounding does not replace the internal calculation.

References

Explicit real-model bounds validate dimensions, inverse branches and discrete controls omitted or approximated in this capture. The international acre is exactly 43560 square international feet; Bookify replaces the rounded captured area factor.

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