ΣM(left pin) = 0 → Right reaction × 6 m – 10 kN × 3 m = 0 → Right = 5 kN ↑ ΣFy = 0 → Left reaction = 5 kN ↑ ΣFx = 0 → Left horizontal = 0.
: AB = +5 kN → Tension (member is being stretched). AC = –7.07 kN → Compression (member is being shortened → risk of buckling).
Joint A (left bottom): Forces: AB (to right), AC (up-right, 45°), reaction 5 kN up. ΣFy = 0: AC·sin45° + 5 = 0 → AC = –7.07 kN (compression). ΣFx = 0: AB + AC·cos45° = 0 → AB = 5 kN (tension).