Figure 2 above shows the state of 2-D stress at a point, p, computed in reference to two different coordinate systems (x-y and x'-y'). As angle alpha between the two coordinate systems increases, the value of sigma'_xx + sigma'_yy
A. Increases compared to sigma_xx + sigma_yy
B. Decreases compared to sigma_xx + sigma_yy
C. Stays the same as sigma_xx + sigma_yy
D. Changes, but it is not a function of alpha
Answer: C
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Biomechanics
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