Free · Triangle calculators 🔺
Isosceles Triangle Area from Equal Leg and Base
Calculate isosceles triangle area from equal leg and base with retained unit controls, positive geometric roots and explicit inverse-branch assumptions.
- Formula & worked example
- Private in your browser
- No signup
Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
Worked inputs Leg (a) = 5, Base (b) = 6 give Height (h) = 4, Area = 12. Values use the initial displayed units.
h² = a²−(b/2)²; A = bh/2
Worked example
Enter these known values and leave the other values blank.
- Leg (a)
- 5 cm
- Base (b)
- 6 cm
- Height (h)
- 4 cm
- Area
- 12 cm²
Assumptions and limitations
- The two equal legs have length a and the unequal base has length b. Positive area requires each leg to exceed half the base.
- Lengths and areas are converted before calculation. Clear an unknown measurement instead of supplying conflicting dimensions.
- Arithmetic uses 64 significant digits and full-precision π. Display rounding and measurement uncertainty are separate from the underlying arithmetic.
Common questions
Which measurements and inverse branch does this model use?
The two equal legs have length a and the unequal base has length b. Positive area requires each leg to exceed half the base.
What happens when the base equals twice an equal leg?
The triangle becomes degenerate with zero height and area. This positive-area model excludes that boundary.
References
The international acre is exactly 43560 square international feet; Bookify replaces the rounded captured area factor.
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