# sin,cos,tan

Trigonometry equalities, inequalities and expressions - sin, cos, tan, cot

### sin,cos,tan

Every time that i do sin,cos or tan in my calculator its the wrong answer. I dont know what it is thats making me get the wrong answer but can somebody help me with how to set it up please?
babyj

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Could you write the problem here, please?

Math Tutor

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Well i have a triangle and the hyp is 15 and one of the angles is 68 one is 90. I dint know how to get another side with just that. Could you help me?

babyj

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So you should use Sine Rule

Always when we have in one triangle 2 angles and one side and search for another side we use Sine Rule.

we have:

$$\frac{a}{sin(A)} = \frac{b}{sin(B)}$$

here we know angles A and B
and the one side too

so the other side is:

$$a = \frac{b.sin(A)}{sin(B)}$$

Do you understand?

Math Tutor

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Yes i do thank you

babyj

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### Re: sin,cos,tan

Yes, you should use sin rule to solve this question.

leesajohnson

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### Re: sin,cos,tan

Yes, you should use sin rule to solve this question...........?????? not good advice

If it is right angled triangle and you know one of the other angles, you can easily calculate the 3 angle, but not even necessary in this case.

Just simply resolve the hypotenuse = 15 into "X and Y" components corresponding to the other 2 sides of the triangle

So... one of the sides is 15 x Sin(68) and the other side is 15 Cos(68)

So that gives.....13.91 and 5.62 ......sum done

I you want to check by Pathagoras Sqrt(13.91^2 + 5.62^2) = 15

And check the angle using Tan .......Arctan(13.91/5.62) = 68
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