If x = a cos θ and y = a cos 2 θ , where a is constant while x , y and θ are variables then d x d y when θ = π is :

Question

If x = a cos θ and y = a cos 2 θ , where a is constant while x , y and θ are variables then d x d y ​ when θ = π is :

TestHub · Accepted Answer

x = a cos θ ⇒ cos θ = a x ​ ​ y = a cos 2 θ = a ( 2 cos 2 θ − 1 ) y = a ( a 2 2 x 2 ​ − 1 ) y = a 2 x 2 ​ − a d x d y ​ = a 4 ​ ⋅ a cos θ = 4 cos θ at θ = π , d x d y ​ = 4 cos π = − 4 ​

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