A pendulum is oscillating in a vertical plane. The acceleration at the extreme position and lowest position are equal. Then the angular amplitude of the pendulum is

acceleration at the extreme position gsinθ  and lowest position v2l . gsinθ=v2l From conservation of energy  12mv2=mgl1−cosθmv2l=2mg1−cosθgsinθ=2g1−cosθsinθ=4sin2θ22sinθ2cosθ2=4sin2θ2tanθ2=12θ2=tan−112θ=2tan−112