Law of Sines Calculator
Solve a triangle with the law of sines from two angles and one side (ASA/AAS).
How it works
- 1Enter angle A, its opposite side a, and angle B.
- 2The law of sines gives side b = a × sin B ÷ sin A.
- 3Angle C is 180° − A − B, and side c follows from the same ratio.
Use cases
- Solve a triangle when you know two angles and a side.
- Find an unknown side from an opposite angle.
- Check trigonometry homework using the sine rule.
Frequently asked questions
What is the law of sines?
In any triangle, a ÷ sin A = b ÷ sin B = c ÷ sin C. Knowing one angle-side pair sets the ratio for the whole triangle.
What inputs does this need?
Two angles (A and B) and the side opposite the first angle (a). The remaining angle and sides are then determined.
Why do my angles need to sum under 180°?
A triangle’s three angles total 180°, so A + B must be less than 180° to leave a positive angle C.
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