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## Main Question or Discussion Point

I am running into an interesting problem on my ti-89 and was wondering if anyone could explain the reason for the following.

I am attempting to solve the following:

[tex] M=\int_{x}^{y}sin(\theta )*(r-a*cos(\theta ))d\theta [/tex]

r = 0.14

a = 0.09

where,

x = 0 deg

y = 120 deg

The calculator gives me an answer of

[tex] M = 10.09838 [/tex]

This answer is incorrect, so I verified that the ti-89 was in degrees (it was) and decided to try the problem in rads instead to see if it is still incorrect.

now where,

x = 0 rad

y = 2*pi/3

I get a correct answer of

[tex] M = 0.17625 [/tex]

What is going on here?

I am attempting to solve the following:

[tex] M=\int_{x}^{y}sin(\theta )*(r-a*cos(\theta ))d\theta [/tex]

r = 0.14

a = 0.09

where,

x = 0 deg

y = 120 deg

The calculator gives me an answer of

[tex] M = 10.09838 [/tex]

This answer is incorrect, so I verified that the ti-89 was in degrees (it was) and decided to try the problem in rads instead to see if it is still incorrect.

now where,

x = 0 rad

y = 2*pi/3

I get a correct answer of

[tex] M = 0.17625 [/tex]

What is going on here?

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