8. Radiusu 18 sm olan çevrodo \( \frac{4}{9} \) radianlıq qövsün uzunluğunu tapın: \( \begin{array}{lll}\text { A) } 8 \mathrm{sm} & \text { B) } 7 \mathrm{sm} & \text { C) } 18 \mathrm{sm} \\ \text { D) } 12 \mathrm{sm} & \text { E) } 10 \mathrm{sm}\end{array} \)

Geometric Mean of 4,2 and 8 is? Select one: a. -2 b. 0 c. 4 d. 9

Cho mặt phăng \( (\alpha) \) và đường thẳng \( d \not \subset(\alpha) \). Khẳng định nào sau đây là sa A. Nếu \( d / /(\alpha) \) thì trong \( (\alpha) \) tồn tại đường thẳng \( \Delta \) sao cho \( \Delta / / d \). B. Nếu \( d / /(\alpha) \) và \( b \subset(\alpha) \) thì \( b / / d \). C. Nếu \( d \cap(\alpha)=A \) và \( d^{\prime} \subset(\alpha) \) thì \( d \) và \( d^{\prime} \) hoặc cắt nhau hoặc chéo nha D. Nếu \( d / / c ; c \subset(\alpha) \) thì \( d / /(\alpha) \).

Q2: \( (8 \) Marks) For the points, \( P(0,1,-1), Q(1,2,0) \), and \( R(1,3,2) \) : A- If \( u=\overline{P Q} \) and \( v=\overline{P R} \), find the vector projection of \( u \) onto \( v \), and the scalar component of \( u \) in the direction of \( v \). B. Find the area of the triangle with vertices \( P, Q \), and \( R \).

Given the equations of lines \( \boldsymbol{l}_{1} \) and \( \boldsymbol{l}_{2} \) are \( \mathrm{r}=(\mathrm{i}+2 \mathrm{j}+3 \mathrm{k})+\lambda(\mathrm{i}-\mathrm{j}+2 \mathrm{k}) \) and \( \mathrm{r}=(5 \mathrm{i}+\mathrm{j}+5 \mathrm{k})+\mu 2 \mathrm{i}+\mathrm{j}-2 \mathrm{k}) \) respectively, where \( \lambda \) and \( \mu \) are real patameters. (a) Show that lines \( \boldsymbol{\ell}_{1} \) and \( \boldsymbol{\ell}_{2} \) intersect and hence, state the coordinates of the point of intersection. (b) Find the Cartesian equation of the plane \( \Pi_{1} \), which contains lines \( \boldsymbol{\ell}_{1} \) and \( \boldsymbol{\ell}_{2} \). (c) The planes \( \Pi_{2} \) and \( \Pi_{3} \) are with equations \( 2 \mathrm{r}+2 \mathrm{y}+z=3 \) and \( 2 \mathrm{r}+p y+2 z=2 \) respectively, where \( p \) is a constant. (i) Find the vector equation of the line of intersection between planes \( \Pi_{1} \) and \( \Pi_{2} \). (ii) Determine the value of \( p \) such that the planes \( \Pi_{1}, \Pi_{2} \) and \( \Pi_{3} \) do not have any common point.

Vhat is the area of the circular ring included between two concentri irclec of radius 14 cm and 10.5 cm ?