Solving trig identities is a little bit guess-and-check. However, here are some clues to narrow down which identities you should try.
Clue 1: 2 Terms Squared2
If you see two terms squared, try a pythagorean identity.
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Clue 2: 1 – something2 or 1 + something2
If you see 1 – something2 or 1 + something2, try a pythagorean identity.
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Clue 3: #something + # or #something – #
If you see #something + # or #something – #, then factor the # out. This also works if it is term*something + term or term*something – term.
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Clue 4: term2 + term + #
If you see a term2 + term + #, try factoring. This also works for term2 – term – # or some variation.
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Clue 5: 1 – something
Difference of squares: If you see a 1 – something, try multiplying it by 1 + something (and vice versa).
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Clue 6: (term A – term B) + (term A + term B)
Difference of squares again: If you see (term A – term B) + (term A + term B), multiply them to get common denominators.
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Clue 7: Reciprocal & Quotient Identities
If all else fails, use the reciprocal identities and quotient identities.
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Solving Trig Identities Printout
That’s it for Solving Trig Identities!
Beyond Solving Trig Identities
For more math resources, visit our Math page. For help with other subjects, visit our Study Tools page!
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