Pretest Questions
I sort of dont know how tp simplify for #10. I am also not sure how to do #16 or 17. For #16, b and c, I dont know how to express the equation. Thanks
posted by melishappy at 10:28 PM
Blog for students in Mr. Karafiol's Period 4 Precalculus BC class to talk about math, learning math, etc.
posted by melishappy at 10:28 PM
2 Comments:
#10 (no calc?) Sin [-] =2x+1
(2x+1)^2+(cos[-])^2=1
(cos[-])^2=1-(2x+1)^2
cos[-]=sqrt(1-(2x+1)^2)
simplifies to sqrt(-4x^2-4x)=cos[-] but we need sec so it is
sec[-]=1/sqrt(-4x^2-4x)
[-]=theta
For 16 the eccentricity of the ellipse will be c/a. Therefore you can find c easily by dividing the distance between the two foci, and a by noting that since the string is 16cm, and the distance between the foci is 10cm, that the semimajor axis is going to be 8.
To solve for theta I just used law of cosines, and got some ugly expression that didn't graph the way I wanted it to.
For 17 I first solved for "a" by plugging in (0,0) and found that it was 0. Then you can solve the strophoid equation with y=tx and find x and y, which are the coordinates of the point in terms of t.
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