86 In un rombo di perimetro 20 cm , la diagonale mag- giore è lunga 8 cm . Determina l'area del rombo. [24 \( \left.\mathrm{cm}^{2}\right] \)

12. G'ildirak aylanasining uzunligi 1,5 m . G'ildirak 20,5 marta aylanganda qancha masofani bosib o'tadi? G'ildirak 231 m masofani bosib o'tganda necha marta aylanadi?

Find equation of straight line through \( (-1,4) \) and perpendicular to the line passing through \( (3,0) \) and \( (1,-2) \).

6. ABCD is a quadrilateral, and AC and BD are its diagonals. Is \( \mathrm{AB}+\mathrm{BC}+\mathrm{CD}+\mathrm{DA}>\mathrm{AC}+\mathrm{BD} \) ? 7. ABCD is a quadrilateral and \( O \) is any point in its interior in the given figure Show that \( A B+B C+C D+D A<2(O A+O B+O C+O D) \).

Find equation of straight line through \( (-1,4) \) and perpendicular to the line passing through \( (3,0) \) and \( (1,-2) \).

Explain the relationship between the area of cross-sections of a three-dimensional shape and its total volume.