130
Areas of
Plane Figures
a² -
(
)
1
2
s
s
d
d
b
a
c
b
a
c
b
a
h
bh
2
=
b
2
√
a² + b² - c²
2b
²
SQUARE
A = area
A =
S²
= 1/2 d²
S = 0.7071d =
√
A
d = 1.414S = 1.414
√
A
RECTANGLE
A = area
A = ab = a
√
d² - a² = b
√
d² - b²
d =
√
a² + b²
a =
√
d² - b² = A ÷ b
b =
√
d² - a² = A ÷ a
RIGHT ANGLED TRIANGLE
A = area
A =
bc
2
a =
√
b² + c²
b =
√
a² - c²
c =
√
a² - b²
ACUTE ANGLED TRIANGLE
A = area
A =
if S = ( a + b + c ) then,
A =
√
S(S -a) (S - b) ( S - c)
