Identify the sum of the interior angle measures of a convex octagon. \( 1080^{\circ} \) \( 1260^{\circ} \) \( 1620^{\circ} \) \( 1440^{\circ} \)

\( =11 \mathrm{~cm}^{2} \) Example 2 The area of a sector of a circle is 38.5 cm if the angle subtended at the centre is 90

4. Which of the following can be the sides of a right triangle? (i) \( 2.5 \mathrm{~cm}, 6.5 \mathrm{~cm}, 6 \mathrm{~cm} \). (iii) \( 2 \mathrm{~cm}, 2 \mathrm{~cm}, 5 \mathrm{~cm} \). (iii) \( 1.5 \mathrm{~cm}, 2 \mathrm{~cm}, 2.5 \mathrm{~cm} \).

3 треугольнике \( A B C \) к стороне \( A B=9 \) см опущена высота, длина которой составила 8 см Найди площадь этого треугольника и дай ответ з квадратных сантиметрах.

Find the area of the sector of a at the centre is \( 140^{\circ} \). (Take \( \pi= \) Solution Area A of a sector is given by; \( \begin{aligned} \text { A }=\frac{\theta}{360} \times \pi r^{2}\end{aligned} \) \( \begin{aligned} \therefore \text { Area } & =\frac{140}{360} \times \frac{22}{7} \times 3^{2} \\ & =11 \mathrm{~cm}^{2}\end{aligned} \)

12-variant 1. \( A(4 ; 3 ;-2), B(-3 ;-1 ; 4), C(2 ; 2 ; 1\} ; \) \( a=\overrightarrow{A B}, b=\overrightarrow{A C}, c=\overrightarrow{C B}, d=2 c-5 b, \quad l=C B, \alpha=4, \beta=3 \)