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Math Help - [SOLVED] Trigonometric problem

  1. #1
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    Exclamation [SOLVED] Trigonometric problem

    Please tell me the solution and the steps required to get solution to this.

    Let sin(a)= 1/ sqrt(5) 0 < a < 90 degrees
    cos(b)= 3/ sqrt(10) 0< b <90

    then what is sin(a+b) equal to?
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  2. #2
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    Take the arcsine and arccosine to find a and b.
    Then plug your a and b into sin(a+b).

    Please be aware that this forum is made to assist you, not just to give you answers.
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  3. #3
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    Quote Originally Posted by Solaris123 View Post
    Please tell me the solution and the steps required to get solution to this.

    Let sin(a)= 1/ sqrt(5) 0 < a < 90 degrees
    cos(b)= 3/ sqrt(10) 0< b <90

    then what is sin(a+b) equal to?

    \sin(a+b) = \sin(a)\cos(b)+\sin(b)\cos(a)

    And

    \sin(a)= \frac{1}{ \sqrt{5}}

     \cos(b)= \frac{3}{ \sqrt{10}}

    To sub into the above formula.

    Use \sin^2a+\cos^2a = \sin^2b+\cos^2b =1

    To find \sin(b) and \cos(a)
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  4. #4
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    Quote Originally Posted by Anonymous1 View Post
    Take the arcsine and arccosine to find a and b.
    Then plug your a and b into sin(a+b).

    Please be aware that this forum is made to assist you, not just to give you answers.
    This exercise is supposed to make the student use trig identities to find an exact answer. Your approach while correct has no great educational purpose.
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  5. #5
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    I must clarify

    I had forgotten to clarify that I must do this all without a calculator, making the suggestion by anonymous kinda mood. I must thanks pickles thought because now I can solve any problem that is similar, I suppose then there are similar identities for say sin(a-b) and the sort, right?
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  6. #6
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    Quote Originally Posted by Solaris123 View Post
    I suppose then there are similar identities for say sin(a-b) and the sort, right?
    Yep, google will tell you what it is!
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