If y ( )= 2 cos ⁡ + cos ⁡2 cos ⁡3 +4 cos ⁡2 +5 cos ⁡ +2, then at = 2 ,y^ ' '+y^ '+y is equal to :

Question

Accepted Answer

Correct answer: C. (c) y= 2 cos ⁡ +2 cos^2 ⁡ -14 cos^3 ⁡ -3 cos ⁡ +8 cos^2 ⁡ -4+5 cos ⁡ +2y= (2 cos^2 ⁡ +2 cos ⁡ -1)(2 cos^2 ⁡ +2 cos ⁡ -1) (2 cos ⁡ +2 )y= 12 ( 11+ cos ⁡ ) ⇒ = 2 y= 12y^ '= 12( -1 (1+ cos ⁡ )^2 (- sin ⁡ )) ⇒ = 2 y= 12y^ ' '= 12 ( cos ⁡ (1+ cos ⁡ )^2- sin ⁡ (2 ) (1+ cos ⁡ ) (- sin ⁡ ) (1+ cos ⁡ )^4 ) ⇒ = 2 y=1

$If y (θ) = \frac{2 cos θ + cos 2 θ}{cos 3 θ + 4 cos 2 θ + 5 cos θ + 2}, then at θ = \frac{π}{2}, y^{’ ’} + y^{’} + y is equal to :$

Solution

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