It activates `Triangle()`

Finally we are at the base case.
When `Triangle()`

`if`

statement causes the
value `1`

to be immediately returned.

The chain of activations is called an **activation chain**.
The picture on this page shows the activation chain when it
has reached the base case.

int Triangle( int N ) { if ( N == 1 ) return 1; else return N + Triangle( N-1 ); }

Now look again at the activation where `N = 2`

`Triangle(1)`

:

2 | int Triangle( int N ) { if ( N == 1 ) return 1; else return N + Triangle( N-1 ); | ------+------- | | 2 1 }