What is the correct expression of equivalent liquid unit weight?

(a) ϒeq.tan^2 [45 – Φ/2]

(b) ϒeq.tan^2 [45 + Φ/2]

(c) ϒeq.tan [45 – Φ/2]

(d) ϒeq.tan [45 + Φ/2]

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