Mind Maps for Trigonometric Ratio: Compound Angles Revision - Class 11, JEE

sin(A+B) = sin A cos B + cos A sin B. This is the most fundamental compound angle identity. Every other addition formula is derived from or parallel to this structure. For JEE, you must also know its companion: sin(A−B) = sin A cos B − cos A sin B, where only the sign between the two terms changes.

JEE Main typically includes 2–3 direct questions from Trigonometric Functions, with compound angle formulas tested in at least one. Based on NTA's official question paper releases from 2021–2024, double angle identities and addition formulas appear most frequently. Questions are usually single-correct or numerical answer type.

Yes, Class 11 NCERT Chapter 3 covers all compound angle identities tested in JEE Main. JEE Advanced may use these identities in deeper problem contexts — particularly in integration and coordinate geometry — so understanding derivations (not just formulas) gives you an edge at that level.

Compound angles involve the sum or difference of two different angles, such as sin(A+B). Multiple angles express a trig function of a multiple of the same angle, such as sin 2A or cos 3A. Multiple angle formulas are actually derived from compound angle formulas by setting B = A, so mastering compound angles first is the correct sequence.

For sin(A+B), the sign matches the operation — sin of a sum gives a plus between the two product terms. For cos(A+B), the sign flips — cos of a sum gives a minus between cos A cos B and sin A sin B. A useful memory anchor: cosine "opposes" addition. This pattern is consistent across all four compound angle formulas.