TRIANGLE SOLVER
CHOOSE RULE • ENTER KNOWN VALUES
RULE + INPUTS
Use NEXT for the answer, then WORKING for full steps.
TRIANGLE ANSWER
MISSING SIDES AND ANGLES
FULL WORKING
RULE • SUBSTITUTION • ANSWER
Use PREVIOUS for the answer, or NEXT for formula help.
TRIANGLE FORMULAS
RIGHT TRIANGLE TRIG
Sine: sinθ = opposite ÷ hypotenuse.
Cosine: cosθ = adjacent ÷ hypotenuse.
Tangent: tanθ = opposite ÷ adjacent.
Use right-triangle mode when the triangle has a 90° angle.
SINE + COSINE RULE
NON-RIGHT TRIANGLES
Sine rule: a ÷ sinA = b ÷ sinB = c ÷ sinC.
Cosine rule: a² = b² + c² − 2bc cosA.
Use sine rule when you know a matching side-angle pair.
Use cosine rule for two sides and the included angle.
WHAT THIS TOOL DOES
SOLVE COMMON TRIANGLE QUESTIONS
This triangle solver calculates missing sides and angles.
It supports right triangles, sine rule and cosine rule questions.
It shows rule choice, substitution and rounded answers.
It is built for GCSE geometry and homework checking.
HOW TO USE
CHOOSE RULE • ENTER VALUES • SOLVE
Choose RIGHT, SINE or COSINE first.
Enter angles in degrees and sides in the same unit.
Use NEXT BOX or tap a field to move through inputs.
Press SOLVE or Enter to calculate.
RIGHT TRIANGLE EXAMPLE
ANGLE AND HYPOTENUSE GIVEN
If θ = 30° and hypotenuse = 10.
Opposite = 10 × sin30 = 5.
Adjacent = 10 × cos30 ≈ 8.66.
The other acute angle is 60°.
SINE + COSINE EXAMPLES
COMMON GCSE CASES
Sine rule: A=40°, B=60°, a=12 gives b≈16.17.
The third angle is C = 180 − 40 − 60 = 80°.
Cosine rule: b=7, c=9, A=30° gives a≈4.57.
Choose the rule that matches the given information.
WHICH RULE?
PICK THE CORRECT METHOD
RIGHT: Use when there is a 90° angle.
SINE: Use with side-angle pairs.
COSINE: Use with two sides and the included angle.
Keep all side lengths in the same unit.
COMMON SEARCHES
SEARCH INTENT COVERAGE
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MORE SEARCHES
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WHO USES IT
STUDENTS • TEACHERS • PARENTS
Students use it for GCSE trigonometry and triangle homework.
Teachers use it to demonstrate which rule fits a question.
Tutors use it for sine rule, cosine rule and SOHCAHTOA revision.
Parents can use it to support triangle maths homework.
RELATED TOOLS
GEOMETRY AND SHAPE LINKS
Triangle solving connects with Pythagoras, trigonometry and area.
FAQ
TRIANGLE SOLVER QUESTIONS
Does it use degrees? Yes, enter all angles in degrees.
Can it solve every triangle? It covers common GCSE cases.
Does it show working? Yes, Page 3 shows the steps.
Can it round answers? Yes, choose 0, 1, 2 or 3 decimal places.
SEARCH TERMS
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