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.
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
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.