represent the share of (a) 4 feddans (c) 18 feddans 3 Two friends invested? ratio of \( 2: 5 \). If the sma profit is 18,000 LE, profit?

(c) \( 20 \% \) of ₹ 90

4) On which interval the function \( f(x)=\frac{1}{\sqrt{1-x^{2}}} \) decreasing: \( \begin{array}{llll}\text { (A) }] 1,+\infty[ & \text { (B) }] 0,1[ & \text { (C) }]-1,0[ & \text { (D) }]-\infty,-1[ \end{array} \)

7) Люддвик XIV-Бур6он

Verify that the equation is an identity. \[ \frac{\csc x}{\cot x}=\sec x \]

12. Si: \( \begin{aligned} x & =\frac{m n}{m+n} \cdot \text { Calcular: } \\ A & =\frac{x+2 m}{2 n-x}-\frac{2 m-x}{x+2 n}+\frac{4 m n}{x^{2}-4 n^{2}}\end{aligned} \)