What's Goniometry ?

Start with graph paper, and a manageable 10 by 10 grid.

Place a corner of grid at origin, 2 sides of grid being x-axis and y-axis.

Take point (2,3); that point is 8 from right side of grid, 7 from top side: see that?

Walk (or draw line) from (2,3) going north-east at 40 degrees:

can you "see" a right triangle with angles 90-50-40?

Carry on...