Home

Triangle Area Using Trigonometry Calculator

Online triangle area calculator: S=½ab·sinC from two sides and the included angle.

展开更多 ▾
S=½ab·sinC
ABCabc
C between a,b
C between a,b
Included angle

📖 Tutorial | Area

1. Definition
Given sides a, b and included angle C, area S=½ab·sinC.
2. Formula & Notation
a,bSides
CIncluded angle
3. Properties & Laws
  • S=½ab·sinC;
  • C=90° gives S=½ab;
  • Equivalent to ½·base·height;
  • Also S=abc/(4R).
4. Steps
  1. Enter a, b, included angle C;
  2. Click "Calculate";
  3. Or click "Load Example".
5. Worked Examples
Example: 5, 6, 30° gives S=½·30·0.5=7.5.
6. Common Pitfalls
C must be between a and b;
Keep the factor ½;
Use sinC, not C.

❓ FAQ | Area

Formula?
S=½ab·sinC.
C?
Included angle.
Right angle?
S=½ab.
Base-height?
Equivalent.
Factor?
½.
Other ways?
Heron's formula.