The figure shows the kinetic energy K of a simple pendulum v

The figure shows the kinetic energy K of a simple pendulum versus its angle ? from the vertical. The vertical axis scale is et by K_s = 30 mJ. The pendulum bob has mass 0.800 kg. What is the length of the pendulum?

My approach was:
30mJ -> .03 J

.03 / (.800)*(9.8)
= .003826 --> .003826/(1-cos (.1rad)) = .765 m But it is wrong

Solution

Max KE of pendulum = max potential energy = m*g*L(1-cos(max_theta))

using graph max KE = 1.5*0.030=0.045

so

0.045 = 0.800*9.8*L*(1-cos(0.100))

L=0.045/(0.800*9.8*(1-cos(0.100)))=1.149m