Question Number 11456 by Joel576 last updated on 26/Mar/17

sin x − cos x = a,  (π/4) ≤ x ≤ (π/2)  Which statement is correct?  (1) sin^2  x − cos^2  x = −(1/2)(√(3 + 2a^2  − a^4 ))  (2) sin^4  x + cos^4  x = (1/8)(−3a^4  + 6a^2  + 5)  (3) sin 2x = ((1 − a^2 )/2)  (4) tan^2  x + cot^2  x = ((−3a^4  − 2a^2  + 8a + 13 )/(2(a^4  + 2a^2  + 1)))

Commented byajfour last updated on 26/Mar/17

none seem to be correct..

Commented byJoel576 last updated on 26/Mar/17

why?

Commented byJoel576 last updated on 26/Mar/17

sorry, in statement (4) it must be tan^2  x + cot^2  x

Answered by ridwan balatif last updated on 26/Mar/17

Answered by ridwan balatif last updated on 26/Mar/17

Commented byJoel576 last updated on 27/Mar/17

thank you very much