Is this correct to use this formula to solve this trigonometry question
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Is this correct to use this formula to solve this trigonometry question

[From: ] [author: ] [Date: 11-09-17] [Hit: ]
You have used a simple method. Dont doubt your answers, there are always many ways to solve maths. Double check your answer using another method or from reverse. Use wolf http://m.wolframalpha.......
Q: Find sin theta given cos theta= 2/5 and sin theta < 0

A: I used this formula:

X^2+ 2^2= 5^2

X^2= 25-4

x= sqrt 21

so sin theta is sqrt21/5

Are these steps correct ? If not could you please solve this step by step. Thanks.

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cosθ=x/r
sinθ=y/r
tanθ=y/x

2^2+y^2=5^2
4+y^2=25
y^2=21
y=√21
sinθ=-√21/5

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Bingo. You have used a simple method. Dont doubt your answers, 'there are always many ways to solve maths'. Double check your answer using another method or from reverse. Use wolf http://m.wolframalpha.com/input/?i=Sine+… . Correct your formula if results are bad. Hope it helps you have fun with math.
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