All 3 Uses

demonstrate
in
Siddhartha
(Edited)

But according to your very own teachings, this unity and necessary sequence of all things is nevertheless broken in one place, through a small gap, this world of unity is invaded by something alien, something new, something which had not been there before, and which cannot be demonstrated and cannot be proven: these are your teachings of overcoming the world, of salvation.†
Chpt 3

demonstrated = showed
He played the game due to a pain of his heart, losing and wasting his wretched money in the game brought him an angry joy, in no other way he could demonstrate his disdain for wealth, the merchants' false god, more clearly and more mockingly.†
Chpt 7 *

demonstrate = show
And after each big loss, his mind was set on new riches, pursued the trade more zealously, forced his debtors more strictly to pay, because he wanted to continue gambling, he wanted to continue squandering, continue demonstrating his disdain of wealth.†
Chpt 7

demonstrating = showing

Definitions:

(1) (demonstrate as in: It demonstrates my point.)
to show
The exact meaning of this sense of demonstrate can depend upon its context. For example:
- "I will demonstrate how to throw a Frisbee." -- show how to do something
- "I will demonstrate how much quicker the new computer is than the old one." -- show how something works
- "Her questioned demonstrated that she was listening and thinking deeply about what was said." -- showed to be true or proved
(2) (demonstrate as in: demonstrate to protest)
a public display supporting a cause -- usually joining with others in a political protest
(3) (meaning too rare to warrant focus)