関連ワード:  1-tan^2x identity    1 tan 2x identity    1/tan^2x identity formula    1 tan 2x trig identity    sqrt 1 tan 2x identity    1 tan 2x pythagorean identity    1 tan 2x sec 2x identity    identity for tan^2x    what does 1-tan^2x equal    is tan^2x-sec^2x=1 an identity