which one is correct??...

errr....just got confused...which one of these is correct??

sin(a) + sin(a+d) + sin(a+2d) + sin(a+3d) + ...... + sin(a+nd) =

\frac{sin\left(\frac{2a+nd}{2}\right)sin\left(\frac{nd}{2} \right)}{sin\left(\frac{d}{2} \right)}

\frac{sin\left(\frac{2a+nd}{2}\right)sin\left(\frac{\left(n+1 \right)d}{2} \right)}{sin\left(\frac{d}{2} \right)} ?

2 Answers

if u want to chek then put n=0 so option b matches.

oh ya....thanx...
silly me...it was so easy to check!!! [3]

√ √ || {} [] () → ~ ^ x x x → → ln log lg lim lim cos sin tan cot arcsin arccos arctan

∫ ∫ ∫ ∫ ∫ ∬ ∬ ∬ ∬ ∬ ∭ ∭ ∭ ∭ ∭ ⨌ ⨌ ⨌ ⨌ ⨌

∑ ∑ ∑ ∑ ∑ ∮ ∮ ∮ ∮ ∮ ∏ ∏ ∏ ∏ ∏ ∐ ∐ ∐ ∐ ∐

+ - × ÷ ± ∓ = ∪ ∩ ≠ ∼ ≈ ∅ ∀ ∃ ∈ ∋ ∝ ≤ ≥ ≃ ≅ ≡ < > ≪ ≫ ⊂ ∉ ⊃ ⊆ ⊇ ⇒ ⇐ ⇔ ⇒ ⇐ ⇔ ⇑ ⇓ ⇕ → ← ↔ → ← ↔ ↑ ↓ ↕ ↖ ↗ ↘ ↙ ↪ ↩ ⇀ ↼ ⇁ ↽

° ∂ ∞ α β γ δ θ λ μ ν ξ π ρ σ φ ω ε ƒ κ τ υ Γ Δ Λ Σ Π Ω