Maths help (1 Viewer)

highshill

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give the exact value for sin(-225)
i am getting sq root 3 / 2 but answer is 1/sq root 2
Why
 

InteGrand

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give the exact value for sin(-225)
i am getting sq root 3 / 2 but answer is 1/sq root 2
Why
Note

sin(-225 deg) = -sin(225 deg) (sin is odd)

= -sin((180-225) deg) (recall the identity sin(180 deg – X) = sin X)

= -sin(-45 deg)

= sin(45 deg)

= 1/(sqrt(2)).
 

highshill

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like my book does not use it, but the answers are a following that identity have i understood the concept wrong
 

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