- A
- B
- C
- D
Step-by-Step Solution
Altitude splits the base into two halves of 3 cm. By Pythagoras, , so cm.
Answer: A)
An equilateral triangle has side 6 cm. What is the length of its altitude?
Class 10Triangles (Similarity)Geometry — Similarity
Key idea: Three similarity criteria
**AA (Angle-Angle)**: Two angles equal → similar. (Third angle is automatic by 180° angle sum.)
**SSS (Side-Side-Side proportionality)**: All three pairs of corresponding sides in same ratio → similar.
**SAS (Side-Angle-Side)**: Two pairs of sides proportional AND included angles equal → similar.
**Important**: SSA does NOT prove similarity (just like for congruence).
AA is by far the most-used in problems: spot two equal angles (often via parallel lines or shared angle) and declare similarity.
**SSS (Side-Side-Side proportionality)**: All three pairs of corresponding sides in same ratio → similar.
**SAS (Side-Angle-Side)**: Two pairs of sides proportional AND included angles equal → similar.
**Important**: SSA does NOT prove similarity (just like for congruence).
AA is by far the most-used in problems: spot two equal angles (often via parallel lines or shared angle) and declare similarity.
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