Law of __: trigonometry equation

Latest answer — September 25, 2026

66 Across

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Clue explained

SINES completes the mathematical name “Law of Sines,” a trigonometric equation relating the sides and angles of a triangle. The plural is part of the established law’s name.

Clue type:
Fill-in-the-blank
A labeled triangle illustrating the Law of Sines

WaPo Crossword

This clue's Friday, September 25, 2026 appearance

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Across

  1. 1Diminish
  2. 5"Too rich for my blood"
  3. 10"My word!"
  4. 14Fusses
  5. 15Bay area on the East Coast
  6. 16Olden times
  7. 17Fit to eat?
  8. 19Enthusiasm
  9. 20Uno e uno e uno
  10. 21Arabian aristocrat
  11. 22Hurled
  12. 24Nintendo princess
  13. 26Archrivals
  14. 28__ Minor
  15. 30Event that may have drawings
  16. 33Single ant, say
  17. 35Hon
  18. 36"Proud Mary" singer Turner
  19. 37"Don't think so"
  20. 38Fit for a king?
  21. 41Nero Wolfe creator Stout
  22. 42Book jacket blurbs
  23. 44Lip-smacking word
  24. 45Air ways
  25. 47Masterful demonstrations
  26. 49Capital city with a Museum of the Viking Age set to open in 2027
  27. 50Home body?
  28. 52Diving aquatic birds
  29. 56One sister in "King Richard"
  30. 58Treadmill setting
  31. 60D.C. MLBer
  32. 61The whole shebang
  33. 62Fit for work?
  34. 65Broccoli __
  35. 66Law of __: trigonometry equation
  36. 67Mud
  37. 68Sudsy mugfuls
  38. 69"Tough crowd!"
  39. 70Zoomed

Down

  1. 1Flounce
  2. 2Be wild about
  3. 3Prize first awarded in 1901
  4. 4Slow start?
  5. 5Object
  6. 6Yacht spot
  7. 7Color gradient technique
  8. 8News initials
  9. 9Rehearsals a cast generally won't stand for?
  10. 10Reason to look one's best?
  11. 11Fit to a tee?
  12. 12Central Asia's North __ Sea
  13. 13Say "It wasn't me," say
  14. 18Start to cry
  15. 23Rough fig.
  16. 25Pair
  17. 27"M'lady"
  18. 29Sarcastic response to rude behavior
  19. 31Individuals
  20. 321-Across opposite
  21. 33Travel as the wind blows
  22. 34Fit for service?
  23. 35Comic book onomatopoeia
  24. 37"SVU" network
  25. 39A second ago
  26. 40Morose
  27. 43Seasonal allergy symptoms
  28. 46Murmur
  29. 48"What We Can Know" novelist McEwan
  30. 49Pontificates
  31. 51Pontificate
  32. 53Ready to pour
  33. 54Inexperienced
  34. 55Place
  35. 56Singer-songwriter Bareilles
  36. 57Bibliography abbr.
  37. 59Paper money
  38. 63Driver's one-eighty
  39. 64Turntable pros

The answer to “Law of __: trigonometry equation” in the The Washington Post crossword is SINES — a 5-letter word. It most recently appeared in the The Washington Post crossword on September 25, 2026, a Friday puzzle, at 66-Across. Below you'll find why that fill fits, every other answer we've recorded for this clue, and links into the puzzle it came from.

“Law of __: trigonometry equation” answer

SINES (5 letters)

Reveal the solution one letter at a time with the tiles above if you'd rather nudge yourself toward it than see the whole word at once. Just want it outright? The answer is SINES.

What does SINES mean?

Reading the plain dictionary sense of SINES is often the fastest way to see why it answers this clue.

(noun)

  • the trigonometric function that is equal to the ratio of the side opposite a given angle (in a right-angled triangle) to the hypotenuse

When else has “Law of __: trigonometry equation” appeared?

The Washington Post reuses clues across dates, sometimes with a different answer depending on the grid. Here's where this exact clue has shown up, and what the answer was each time — handy when you're checking whether today's fill is the only one.

September 25, 2026 (most recent) → SINES. We haven't indexed another appearance of this exact clue yet.

Frequently asked questions

What is the answer to “Law of __: trigonometry equation”?

The answer is SINES, a 5-letter word. It most recently appeared in the The Washington Post crossword on September 25, 2026.

How many letters is the answer to “Law of __: trigonometry equation”?

5 letters: SINES.

When did this clue appear?

Most recently in the The Washington Post crossword on September 25, 2026 (a Friday puzzle), at 66-Across.

Can “Law of __: trigonometry equation” have a different answer?

Yes — The Washington Post sometimes reuses a clue with a different solution to fit the grid. The answers we've recorded for each date it appeared are listed above when available.

Where can I find the rest of this day's WaPo Crossword answers?

The full grid for September 25, 2026 is on the WaPo Crossword answers page, with every clue and answer from that puzzle.

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