250–(542÷410+42) = 250–(516÷410+42) Step 1 = 250–(80÷410+42) Step 2 = 250–(80÷40+42) Step 3 = 250–(2+42) Step 4 = 250–44 Step 5 = 206 Step 6

is there supposed to be a picture here?

place r′ so that qr′ is parallel to the tangent.

now we get that ∠r′py=∠pr′q, where y is on the tangent, on the opposite side of p from x.

also, because of the symmetry, ∠r′py=∠qpx.

finally, note that no matter where we place r, as long as it's on the correct arc, we have ∠prq=∠pr′q.

stringing all these equalities together, we end up with ∠prq=∠qpx.

this picture will show how its going to look like.

hope this by jack monhen