Grade 11Trigonometry
What is the value of tan6 π/9 – 33 tan4 π/9 + 27 tan2 π/9?
What is the value of tan6 π/9 – 33 tan4 π/9 + 27 tan2 π/9?
3 Answers
Arun
Approved Tutor Answer6 Years agoUse triple angle formula:
tan(3x) = (3 tan(x) − tan³(x)) / (1 − 3 tan²(x))
(3 tan(π/9) − tan³(π/9)) / (1 − 3 tan²(π/9)) = tan(π/3)
(3 tan(π/9) − tan³(π/9)) / (1 − 3 tan²(π/9)) = √3
(3 tan(π/9) − tan³(π/9)) = √3 (1 − 3 tan²(π/9))
Square both sides:
(3 tan(π/9) − tan³(π/9))² = 3 (1 − 3 tan²(π/9))²
tan⁶(π/9) − 6 tan⁴(π/9) + 9 tan²(π/9) = 3 (9 tan⁴(π/9) − 6 tan²(π/9) + 1)
tan⁶(π/9) − 6 tan⁴(π/9) + 9 tan²(π/9) = 27 tan⁴(π/9) − 18 tan²(π/9) + 3
tan⁶(π/9) − 6 tan⁴(π/9) − 27 tan⁴(π/9) + 9 tan²(π/9) + 18 tan²(π/9) = 3
tan⁶(π/9) − 33 tan⁴(π/9) + 27 tan²(π/9) = 3
Vikas TU
Approved Tutor Answer6 Years agoDear student
For short cut you can you this link
Good Luck
TEJA KRISHNA
tan(3x) = (3 tan(x) − tan³(x)) / (1 − 3 tan²(x))
(3 tan(π/9) − tan³(π/9)) / (1 − 3 tan²(π/9)) = tan(π/3)
(3 tan(π/9) − tan³(π/9)) / (1 − 3 tan²(π/9)) = √3
(3 tan(π/9) − tan³(π/9)) = √3 (1 − 3 tan²(π/9))
Square both sides:
(3 tan(π/9) − tan³(π/9))² = 3 (1 − 3 tan²(π/9))²
tan⁶(π/9) − 6 tan⁴(π/9) + 9 tan²(π/9) = 3 (9 tan⁴(π/9) − 6 tan²(π/9) + 1)
tan⁶(π/9) − 6 tan⁴(π/9) + 9 tan²(π/9) = 27 tan⁴(π/9) − 18 tan²(π/9) + 3
tan⁶(π/9) − 6 tan⁴(π/9) − 27 tan⁴(π/9) + 9 tan²(π/9) + 18 tan²(π/9) = 3
tan⁶(π/9) − 33 tan⁴(π/9) + 27 tan²(π/9) = 3
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