maximum tension in the string of an oscillating pendulum is double of the minimum tension. Then angular amplitude is

Answer 1

Tension at the bottom is

mg+mv^2/r

Tension at the high point is

mg*cosTheta

2*mgCosTheta=mg+mv^2/r

but 1/2 mv^2= mgr(1-cosTheta)

2mgCosTheta=mg+2mg(1-cosTheta)

cosTheta(2mg+2mg)=mg
cosTheta= 1/4

Theta= arcCos .25

And that is amplitude.