- A∠A
- B∠B
- C∠C
- DAll three are equal
Step-by-Step Solution
The largest angle is opposite the longest side. The longest side is CA (9 cm), and the angle opposite CA is ∠B.
Answer: B) ∠B
In ΔABC, AB = 5 cm, BC = 7 cm and CA = 9 cm. Which is the largest angle?
Class 9Triangles (Congruence)Geometry — Triangles
Key idea: The four valid congruence criteria
**SSS**: All three sides equal → congruent.
**SAS**: Two sides + included angle equal → congruent.
IMPORTANT: the angle must be BETWEEN the two given sides. SSA (two sides + non-included angle) is NOT a valid criterion in general.
**ASA**: Two angles + included side equal → congruent.
**AAS**: Two angles + a non-included side equal → congruent (since the third angle is forced by 180°).
**RHS** (right triangles only): Right angle + hypotenuse + one side equal → congruent.
**Once congruent, all corresponding parts are equal (CPCT)** — that's the lemma you cite to extract any matching side or angle in the next step of a proof.
**SAS**: Two sides + included angle equal → congruent.
IMPORTANT: the angle must be BETWEEN the two given sides. SSA (two sides + non-included angle) is NOT a valid criterion in general.
**ASA**: Two angles + included side equal → congruent.
**AAS**: Two angles + a non-included side equal → congruent (since the third angle is forced by 180°).
**RHS** (right triangles only): Right angle + hypotenuse + one side equal → congruent.
**Once congruent, all corresponding parts are equal (CPCT)** — that's the lemma you cite to extract any matching side or angle in the next step of a proof.
Master this chapter in 30 minutes a day.
Don't just memorise the answer — build a daily practice habit.
Practice 5 Similar Questions Free →All Triangles (Congruence) practice questions
More Class 9 Triangles (Congruence) practice
True or False: If the three angles of one triangle equal the three angles of another,…Which set of side lengths can form a triangle?In ΔPQR, the bisector of ∠P meets QR at S, and PQ = PR. State the criterion proving ΔPQS…How many integer values can the third side of a triangle take if the other two sides are…In ΔABC, ∠B = ∠C. Which sides are equal?