If sin theta + cosec theta = 1/2, then the value of sin4 + cos4
Answers
sin⁴θ + cos⁴θ = 1
it is given that, sinθ + cosecθ = 1/2
then we have to find the value of sin⁴θ + cos⁴θ
first of all, sinθ + cosecθ ≥ 1 or, ≤ -1.
given statement is wrong.
it should be,
sinθ + cosecθ = 2 ( in place of 1/2)
so, sinθ + 1/sinθ = 2
⇒sin²θ - 2sinθ + 1 = 0
⇒(sinθ - 1)² = 0
⇒sinθ = 1
and we know, if sinθ =1 then, cosθ = 0
because, sin²x + cos²x = 1 [ trigonometric identity ]
then, sin⁴θ + cos⁴θ = (1)⁴ + (0)⁴ = 1
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Correct Question :-------- sin@ + cosec@ = 2
we have to Find = sin⁴@ + cos⁴@ ?
we know that,
cosec@ = 1/sin@
so,
sin@ + 1/sin@ = 2
sin²@ +1 = 2sin@
sin²@ -2sin@ +1 = 0
a² - 2ab + b² = (a-b)²
so, we get,
(sin@-1)² = 0
sin@ = 1
That means in
sin²@ + cos²@ = 1
we have cos²@ = 0
so,
sin⁴@ + cos⁴@ = (1)⁴ + (0)⁴ = 1 (Ans)
Remember :-------
when sinx + cosecx = 2
sin^n x + cosec^n x = 2 (Always)