Free · Algebra and geometric models

Trapezoid Perimeter with Missing-Leg Alternatives

Calculate perimeter and recover a missing trapezoid leg from bases, the other leg and a base angle.

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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, Perimeter (P) = 20.

P=a+b+c+d; missing leg²=h²+remaining horizontal offset²

Worked example

Enter these known values and leave the other values blank.

a (base)
8 cm
b (base)
2 cm
c (side)
5 cm
d (side)
5 cm
Perimeter (P)
20 cm

Assumptions and limitations

  • Bases and legs are positive. When a slope mode is used, a is the longer base.
  • The captured missing-leg expression selects a positive distance; positive and negative horizontal offsets share that length.

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.

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