What is the angle between the direction of $A$ and the positive direction of x?











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The x component of vector $A$ is 25.0 m and the y component is 40.0 m. (a) What is the magnitude of $A$? (b) What is the angle between the direction of $A$ and the positive direction of x?




I solved (a). When attempting (b) I tried using the formula $tantheta=frac{a_y}{a_x}=frac{40}{-25}=-1.6$, thus $arctan(-1.6)=-58º$ but the answer key is $122º$.



Any help is appreciated.






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    The x component of vector $A$ is 25.0 m and the y component is 40.0 m. (a) What is the magnitude of $A$? (b) What is the angle between the direction of $A$ and the positive direction of x?




    I solved (a). When attempting (b) I tried using the formula $tantheta=frac{a_y}{a_x}=frac{40}{-25}=-1.6$, thus $arctan(-1.6)=-58º$ but the answer key is $122º$.



    Any help is appreciated.






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      up vote
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      The x component of vector $A$ is 25.0 m and the y component is 40.0 m. (a) What is the magnitude of $A$? (b) What is the angle between the direction of $A$ and the positive direction of x?




      I solved (a). When attempting (b) I tried using the formula $tantheta=frac{a_y}{a_x}=frac{40}{-25}=-1.6$, thus $arctan(-1.6)=-58º$ but the answer key is $122º$.



      Any help is appreciated.






      vectors







      share|cite|improve this question














      The x component of vector $A$ is 25.0 m and the y component is 40.0 m. (a) What is the magnitude of $A$? (b) What is the angle between the direction of $A$ and the positive direction of x?




      I solved (a). When attempting (b) I tried using the formula $tantheta=frac{a_y}{a_x}=frac{40}{-25}=-1.6$, thus $arctan(-1.6)=-58º$ but the answer key is $122º$.



      Any help is appreciated.






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      asked Sep 27 at 20:15









      Mauricio Mendes

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          It appears that you might mean for the point to be (-25,40) although you stated (25,40). The atan2(y,x) function using (-25,40) will yield ~122 deg.






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            It appears that you might mean for the point to be (-25,40) although you stated (25,40). The atan2(y,x) function using (-25,40) will yield ~122 deg.






            share|cite|improve this answer

























              up vote
              0
              down vote













              It appears that you might mean for the point to be (-25,40) although you stated (25,40). The atan2(y,x) function using (-25,40) will yield ~122 deg.






              share|cite|improve this answer























                up vote
                0
                down vote










                up vote
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                It appears that you might mean for the point to be (-25,40) although you stated (25,40). The atan2(y,x) function using (-25,40) will yield ~122 deg.






                share|cite|improve this answer












                It appears that you might mean for the point to be (-25,40) although you stated (25,40). The atan2(y,x) function using (-25,40) will yield ~122 deg.







                share|cite|improve this answer












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                share|cite|improve this answer










                answered Sep 27 at 21:40









                Narlin

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