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# Keplers 1st Law watch

1. Assuming that the sun lies at the principal focus of the solar system, and given that the semi-major axis and eccentricity of Mars is 1.5237 AU and 0.0934 respectively, calculate:

The distance (in AU) when Mars is closest to the Sun (known as perihelion). The angle θ=0°
r = a(1 - e^2) / (1 +e cos θ)

The correct solution is 1.38 AU

Though if I use the above eqn putting a=1.5237 and e=0.0934 I get an answer of 16.17.

Thanks for any help!
2. (Original post by little pixie)
Assuming that the sun lies at the principal focus of the solar system, and given that the semi-major axis and eccentricity of Mars is 1.5237 AU and 0.0934 respectively, calculate:

The distance (in AU) when Mars is closest to the Sun (known as perihelion). The angle θ=0°
r = a(1 - e^2) / (1 +e cos θ)

The correct solution is 1.38 AU

Though if I use the above eqn putting a=1.5237 and e=0.0934 I get an answer of 16.17.

Thanks for any help!
I don't know why, quick substitution and the answer is what I get. You must be entering it into your calculator wrong.
3. I got it that time! Don't know what I was doing wrong...!

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