# Calculate total harmonic distortion

I have the following problem.

MY ATTEMPT

I found the formula for the total harmonic distortion to be this:

$$\THD = \frac{\sqrt{V_2^2+V_3^2+V_4^2+V_5^2+...}}{V_1} \$$, where the subscript denotes the harmonic.

Looking at the spectrum above, it seems like I'm supposed to make the following conclusions: V1 = 18.9241, V2 = -67.363, V3 = -8.5635, V4 = -61.8046, V5 = -13.3634.

Inserting these values in the formula gives me a result of $$\THD = 4.90 \$$ which doesn't seem reasonable at all, I must be doing something wrong. I'm also unsure of where I'm supposed to use the information about the forward voltage of the diode.

I hope someone can help me or clarify things for me.