Reduce number of operations in `Triangle::circumscribed_circle` #717

Job	Run time
cargo check (msrv) (wasm32)	24s
cargo clippy (wasm32)	38s
cargo clippy (windows-latest)	1m 4s
cargo check (msrv) (windows-latest)	47s
cargo clippy (macos-latest)	46s
cargo doc	38s
cargo check (msrv) (macos-latest)	42s
cargo clippy (ubuntu-latest)	41s
formatting	27s
cargo check (msrv) (ubuntu-latest)	32s
cargo test (windows-latest)	46s
cargo test (wasm32)	21s
cargo test (macos-latest)	33s
typos	3s
cargo test (ubuntu-latest)	19s
	8m 41s

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