Triangles
Uttarakhand Board · Class 9 · Mathematics
Flashcards for Triangles — Uttarakhand Board Class 9 Mathematics. Quick Q&A cards covering key concepts, definitions, and formulas.
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See them allWhat is a triangle? Define its basic components.
Answer
A triangle is a closed figure formed by three intersecting lines. It has three sides, three angles, and three vertices. For example, in triangle ABC: AB, BC, CA are the three sides; ∠A, ∠B, ∠C are the…
What are congruent figures? Give examples from daily life.
Answer
Congruent figures are figures that have the same shape and size. They can cover each other completely when placed on top of each other. Examples: two coins of the same denomination, identical photogra…
When are two triangles said to be congruent? What does the symbol ≅ mean?
Answer
Two triangles are congruent if all corresponding sides and angles are equal. The symbol ≅ means 'congruent to'. If △PQR ≅ △ABC, then PQ = AB, QR = BC, RP = CA and ∠P = ∠A, ∠Q = ∠B, ∠R = ∠C.
What is the correct way to write congruence of triangles? Why is correspondence important?
Answer
When writing congruent triangles, the order of vertices must show the correct correspondence. If P↔A, Q↔B, R↔C, then we write △PQR ≅ △ABC. Writing △QRP ≅ △ABC would be incorrect because it doesn't sho…
What does CPCT stand for and when is it used?
Answer
CPCT stands for 'Corresponding Parts of Congruent Triangles'. It is used to state that when two triangles are congruent, their corresponding sides and angles are equal. This is often used in proofs af…
State the SAS congruence rule (Axiom 7.1).
Answer
SAS Congruence Rule: Two triangles are congruent if two sides and the included angle of one triangle are equal to the two sides and the included angle of the other triangle. The angle must be between …
Why doesn't the SSA or ASS rule work for triangle congruence?
Answer
SSA (Side-Side-Angle) or ASS rule doesn't work because the angle is not included between the two equal sides. Two triangles can have two sides and one angle equal but still not be congruent if the ang…
State the ASA congruence rule (Theorem 7.1).
Answer
ASA Congruence Rule: Two triangles are congruent if two angles and the included side of one triangle are equal to two angles and the included side of the other triangle. The side must be between the t…
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