CHALLENGE

ACTIVITY

$1\mathrm{.}7\mathrm{.}1$: Complete the program to print out a filled triangle four lines high.

$587030\mathrm{.}4599812.q3zqy7$

Complete the program below to print out a filled triangle four lines high. In other words, the output of this program should match the following, exactly:

$x$

$xx$

$xxx$

$x$

$\frac{?}{?}$#include

using namespace $std$;

int main$()$

cout