Answer: √13.
- A √7
- B √13
- C 2√3
- D √11
Correct answer: B. √13
Explanation: a² = b² + c² - 2bc cosA = 9 + 16 - 2×3×4×(1/2) = 25 - 12 = 13. a = √13.
Unit circle with standard angles 0, 30, 45, 60, 90 degrees; at 45 degrees the point is (cos45, sin45) = (1/sqrt2, 1/sqrt2).
Concept context
Ratios, identities, and applications in triangles