Question

Llercise 5B
(b) BC = 16 cm and 1 from vertex A = 1.2
2. Find the area of an equilateral triangle, whose sides are:
(a) 5 cm
(b) 7 cm
(c) 8.5 cm
(d) 12.2 cm
(a) l = 7 cm, b = 5 cm
(c) l= 3.9 cm, b = 1.2 cm
(b) l = 8 cm, b = 7 cm
(d) 1 = 7.3 cm, b = 1.5 cm
(a) 7 cm (b) 9 cm
(c) 12 cm (d) 15 cm (e) 21 cm (£) 25 cm (g) 27 cm
1. Find area of the triangle AABC, where
(a) BC = 7 cm, I from vertex A=4 cm
(c) Base is 2.4 cm and I from vertex is 1.4 cm (d) Base is 7 cm and I from vertex is 8 cm
3. Find the area of the rectangle whose dimensions are given below.
4. Find the area of the square whose side is:​

Answer 1

$\small { \sf{Area \: of \: an \: equilateral \: triangle , A = \frac{ \sqrt{3} }{4} \times Side²}}$

$\small \sf{(a) \: 5 \: cm}$

$\small \sf{A = \frac{ \sqrt{3} }{4} \times {5}^{2} }$

$\small \sf{A = \frac{ \sqrt{3} }{4} \times 25}$

$\small \sf{A = \frac{25 \sqrt{3} }{4} }$

$\small \sf{A = \frac{ 25 \times 1.732 }{4} }$

$\small \sf{A = \frac{ 43.3 }{4} = 10.825 \: cm}$

$\sf{(b) \: 7 \: cm }$

$\small \sf{A = \frac{ \sqrt{3} }{4} \times {7}^{2} }$

$\small \sf{A = \frac{ \sqrt{3} }{4} \times 49 }$

$\small \sf{A = \frac{ 49\sqrt{3} }{4} }$

$\small \sf{A = \frac{{49 \times 1.732} }{4}}$

$\small \sf{A = \frac{ 84.868}{4} =21.217 \: cm }$

$\small\sf{ (c) \: 8.5 \: cm}$

$\small \sf{A = \frac{ \sqrt{3} }{4} \times {8.5}^{2} }$

$\small \sf{A = \frac{ \sqrt{3} }{4} \times 72.25}$

$\small \sf{A = \frac{ 72.25\sqrt{3} }{4} }$

$\small \sf{A = \frac{ 72.25 \times 1.732 }{4} }$

$\small \sf{A = \frac{ 125.137}{4} = 31.28425 \: cm }$

$\small \sf{(d) \:12.2 \: cm }$

$\small \sf{A = \frac{ \sqrt{3} }{4} \times {12.2}^{2} }$

$\small \sf{A = \frac{ \sqrt{3} }{4} \times 148.84 }$

$\small \sf{A = \sqrt{3} \times 37.21}$

$\small \sf{A = 1.732 \times 37.21 }$

$\small \sf{A = 64.44772 \: cm }$