Question
If 5cos²A + 2sin²A = 13/3, then find the value of (sec²A - 1)
Solution
5cos²A + 2sin²A = 13/3
Or, 3cos²A + 2(cos²A + sin²A) = 13/3
Or, 3cos²A + 2 = 13/3
Or, 3cos²A = 13/3 - 2 = 7/3 => cos²A = 7/9
So, sec²A = 1 / (7/9) = 9/7
Required value = 9/7 - 1 = 2/7
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