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Thread: Maths help

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    Member highshill's Avatar
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    Maths help

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

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    Re: Maths help

    Quote Originally Posted by highshill View Post
    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)).
    bujolover likes this.

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    Re: Maths help

    so when do i apply these identities

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    Re: Maths help

    Quote Originally Posted by highshill View Post
    so when do i apply these identities
    You can use them to get the given angle down to a number that you known the exact trig. value of.

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    Re: Maths help

    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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    Re: Maths help

    Quote Originally Posted by highshill View Post
    like my book does not use it, but the answers are a following that identity have i understood the concept wrong
    Is it Maths In Focus?
    integral95, Esse and He-Mann like this.

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    Re: Maths help

    yes

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    Re: Maths help

    Quote Originally Posted by integrand View Post
    is it maths in focus?
    hhahahahha
    HSC 2016:

    English Advanced [90] • Mathematics [95] • Mathematics Extension 1 [92] • Chemistry [92] • Business Studies [95] • Economics [91]

    98.65 (All-Rounders)

    B. Information Systems/B. Comm @ UNSW '20

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