Help in gnuplot, what commands should I enter to plot 4 graphs?

Question

infographics

1. Graph a function given parametrically
2. Graph a function given in a polar coordinate system
3. Graph a function in a Cartesian coordinate system
4. Graph a function given parametrically

Answer 1

What's the problem?
for example, the first graph can be plotted with the command
plot x**3/8+x**2-cos(2*x)
Result: