Numerically approximate arc perimeter #681

Job	Run time
cargo clippy (wasm32)	43s
cargo check (msrv) (windows-latest)	1m 10s
cargo clippy (windows-latest)	1m 25s
cargo check (msrv) (wasm32)	20s
cargo check (msrv) (macos-latest)	29s
cargo clippy (macos-latest)	43s
cargo doc	24s
cargo clippy (ubuntu-latest)	41s
cargo check (msrv) (ubuntu-latest)	24s
cargo fmt	22s
cargo test (windows-latest)	1m 6s
typos	7s
cargo test (macos-latest)	29s
cargo test (wasm32)	20s
cargo test (ubuntu-latest)	20s
	9m 3s

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