JEE Mains Maths · Teaching notes

Properties of Triangle — JEE Mains Mathematics

Properties of Triangle has 11 past-year questions from 2021 to 2024, five of them with a numerical answer. They use the sine and cosine rules, conditions on the angles, and the area with the two radii. Most take a few lines once the right relation is chosen, so the page is about recognising which one the data point to.

Every subtopic, worked example, formula and trap in one printable document — answers shown, ready to share.

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Subtopic notes

Solution of Triangles
11 PYQs
Relating the sides and angles of a triangle through the sine and cosine rules, and its area to the radii of its incircle and circumcircle.

Formula & revision sheet

3 formulas · 3 gotchas across all subtopics — the exam-eve cheat-sheet

Solution of Triangles

Formulas (3)

The sine and cosine rules · Cosine rule $a^2=b^2+c^2-2bc\cos A$
Conditions on the angles · Sines to sides $\sin A=\frac{a}{2R}$
Area, inradius and circumradius · The two radii $r=\frac{\Delta}{s},\qquad R=\frac{abc}{4\Delta}$

Watch out for (3)

Check both roots
→ The sine and cosine rules
sin 2A = sin 2B has two cases
→ Conditions on the angles
Semi-perimeter, not perimeter
→ Area, inradius and circumradius

PYQ weightage by concept

3 concepts · 11 PYQs — where the marks actually sit, so you know what to drill first

Solution of Triangles11 PYQs · 100%

Concept	PYQs	Share
The sine and cosine rules	5	45%
Conditions on the angles	3	27%
Area, inradius and circumradius	3	27%

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