表达式2: "r" equals StartFraction, 3 "a" sin left parenthesis, theta , right parenthesis cos left parenthesis, theta , right parenthesis Over sin squared left parenthesis, theta , right parenthesis sin left parenthesis, theta , right parenthesis plus cos squared left parenthesis, theta , right parenthesis cos theta , EndFractionr=3asinθcosθsin2θsinθ+cos2θcosθ
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定义域\theta最小值:
less than or equal to theta less than or equal to≤θ≤