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Triangle Solver (SSS/SAS/ASA)

Solve triangles using SSS, SAS, or ASA methods. Calculate missing side lengths and angles using the Law of Sines and Cosines.

Key Formula

Law of Cosines: c^2 = a^2 + b^2 - 2ab * cos(C) Law of Sines: a / sin(A) = b / sin(B) = c / sin(C) Angle Sum: A + B + C = 180°

Where:

a, b, c= Sides of the triangle
A, B, C= Angles opposite respective sides (in degrees)

Example

Given sides a = 7, b = 10, and c = 5 (SSS), find all angles of the triangle.

1: Use the Law of Cosines to find angle A: A = arccos((b² + c² - a²) / 2bc).

2: Calculate angles B and C similarly using the Law of Cosines.

3: Verify that the sum of angles equals 180°.

Result: Angles calculated are approximately A = 28.0724°, B = 58.2825°, and C = 93.6451°.

Understanding Triangle Solver (SSS/SAS/ASA)

The Triangle Solver (SSS/SAS/ASA) is a powerful mathematical tool designed to find unknown sides and angles of a triangle when certain measurements are known. It supports three fundamental methods: Side-Side-Side (SSS), Side-Angle-Side (SAS), and Angle-Side-Angle (ASA). Each method uses specific sets of inputs to determine the complete triangle.

The SSS method requires all three sides to be known and calculates the angles using the Law of Cosines. The SAS method uses two sides and the included angle to find the remaining side and angles. The ASA method involves two angles and the included side, applying the Law of Sines to solve the triangle.

This solver ensures precision by validating inputs and applying trigonometric laws accurately. It is an essential tool for students, educators, engineers, and anyone working with geometric problems involving triangles.

Formula

Law of Cosines:
c^2 = a^2 + b^2 - 2ab * cos(C)
A = arccos((b^2 + c^2 - a^2) / (2bc))
B = arccos((a^2 + c^2 - b^2) / (2ac))
C = arccos((a^2 + b^2 - c^2) / (2ab))

Law of Sines:
a / sin(A) = b / sin(B) = c / sin(C)

Angle Sum:
A + B + C = 180°

FAQ

  • What is the Triangle Solver (SSS/SAS/ASA) tool used for?

    The Triangle Solver tool calculates unknown sides and angles of a triangle when given specific sets of inputs. It supports three common methods: SSS (three sides), SAS (two sides and included angle), and ASA (two angles and included side). This helps in solving triangles accurately using trigonometric laws.

  • How does the Law of Cosines apply in triangle solving?

    The Law of Cosines relates the lengths of sides of a triangle to the cosine of one of its angles. It is especially useful in the SSS and SAS cases to find unknown angles or sides. The formula is c² = a² + b² - 2ab cos(C), allowing calculation of a side or angle when others are known.

  • When should I use the Law of Sines in triangle calculations?

    The Law of Sines is applied when you know either two angles and one side (ASA) or two sides and a non-included angle (AAS or SSA). It states that the ratio of a side length to the sine of its opposite angle is constant across the triangle, enabling calculation of missing sides or angles.

  • What are common errors to avoid when using this solver?

    Ensure that inputs are positive and angles are between 0° and 180°. The triangle inequality theorem must be satisfied for side lengths. Also, be cautious of ambiguous cases in SSA (not covered here). Incorrect inputs may lead to invalid or no solutions, which the solver will warn about.

Important — Educational Use Only

This calculator is provided for educational and informational purposes only. The results are estimates based on the information you provide and should not be considered financial, legal, or professional advice.

No Warranty: SmartKitNow makes no warranties regarding the accuracy, completeness, or reliability of the calculations. Results may vary based on individual circumstances, market conditions, and other factors.

Professional Advice: Always consult with qualified professionals (financial advisors, accountants, attorneys, or other specialists) before making any important financial or legal decisions.

Limitation of Liability: SmartKitNow and its affiliates are not liable for any losses, damages, or consequences resulting from the use of this calculator or reliance on its results.

By using this calculator, you acknowledge that you have read and understood this disclaimer, and you agree to use the tool at your own risk. For personalized guidance tailored to your specific situation, please seek advice from a qualified professional in the relevant field.

📋Last updated: August 2026

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