Math Is Fun Forum

sanya

Guest

can u pls solve this problems for me help me

find the values of y in the following equqtions
(1) siny=cos48degree
(2) cos(90-y)=sin56degree47
(3) find the value of sin 0,and cos0,if tan0 equal to 43

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: can u pls solve this problems for me help me

A useful thing to know here is that siny = cos(90-y).

So in the first question you can say that cos(90-y) = cos48 and work from there.
I'm not sure exactly what the second question is saying, but I'm guessing that you can turn the cos(90-y) into siny to make things simpler.

The third question is a little harder. tanθ = sinθ/cosθ, so if tanθ = 43, then sinθ = 43cosθ.

Also, sin²θ + cos²θ = 1, for any value of θ.
Hence, (43cosθ)² + (cosθ)² = 1.
1850cos²θ = 1
cosθ = √(1/1850).

You can find sinθ by using that result and the bolded equation.

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Why did the vector cross the road?
It wanted to be normal.

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: can u pls solve this problems for me help me

And in case you didn't know,  -1 ≤ sinθ ≤ 1 and -1 ≤ cosθ ≤ 1.
"Unit Circle" is good to know.
http://www.sparknotes.com/testprep/book … ion5.rhtml

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