📐
幾何学計算機
図形の面積・周長計算【無料】三角形・四角形・円・多角形の面積と周の長さを即計算。頂点ドラッグで形状変更・内接円・外接円・ヘロンの公式など公式集付き。
Geometry Calculator
Unit:
Input Method
Results
Right TriangleScalene
Side a / Side b / Side c
3 / 4 / 5 cm
Angle A (°) / Angle B (°) / Angle C (°)
36.87° / 53.13° / 90°
Area
6 cm²
S = √(s(s-a)(s-b)(s-c))
Perimeter
12 cm
Inradius r
1 cm
r = S/s
Circumradius R
2.5 cm
R = abc/(4S)
Drag vertices to reshape
Centroid
Circumcenter
Incenter
Orthocenter
📖How to Use
- 1Select a shape (triangle, circle, polygon, solid, etc.)
- 2Enter parameters such as side lengths or radius
- 3Calculate area, perimeter, volume, surface area, and more
💡Tips & Knowledge
- •Heron's formula: with sides a, b, c, area S = √(s(s-a)(s-b)(s-c)) where s=(a+b+c)/2
- •Circle area = πr², circumference = 2πr. π ≈ 3.14159265... (irrational, non-repeating)
- •The golden ratio (φ ≈ 1.618) is the ratio of a pentagon's diagonal to its side, and appears widely in nature, architecture, and design
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