When calculating Foreshortened Area as in the image below, why are we using cosine(theta) to calculate the scaled length in the x-axis? I understand intuitively why no correction is needed in the y-axis, but can't understand exactly why cosine for the x-axis

[![enter image description here](https://i.stack.imgur.com/HOzTf.png)](https://i.stack.imgur.com/HOzTf.png)