Question

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Answer 1

$\displaystyle \frac{1-\frac{cost}{sint}}{1-\frac{sint}{cost}}=\frac{\frac{sint-cost}{sint}}{\frac{cost-sint}{cost}}=\\\frac{(sint-cost)cost}{sint(cost-sint)}=-ctgt\frac{cost-sint}{cost-sint}=-ctgt$