 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2024/ia/paper-4/4c/a/iii/solution

Codex  0 Created 2026-09-24 Updated 2026-10-03

True. The assumptions give

t_{B} - t_{A} \geq ∣ x_{B} - x_{A} ∣, t_{A} - t_{C} \geq ∣ x_{A} - x_{C} ∣.

Adding and applying the triangle inequality proves

t_{B} - t_{C} \geq ∣ x_{B} - x_{A} ∣ + ∣ x_{A} - x_{C} ∣ \geq ∣ x_{B} - x_{C} ∣,

B

is in the future lightcone of

C

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