B H = B Q + Q P + P H = BH=BQ+QP+PH= B H = BQ + QP + P H =
= 54.5 + 17.5 + 36 = 108 =54.5+17.5+36=108 = 54.5 + 17.5 + 36 = 108 The right triangle A P H APH A P H
Let A H = x , ∠ P A H = α . AH=x, \angle PAH=\alpha. A H = x , ∠ P A H = α . Then tan ( α ) = P H A H = 36 x \tan(\alpha)=\dfrac{PH}{AH}=\dfrac{36}{x} tan ( α ) = A H P H = x 36
The right triangle A B H ABH A B H
tan ( 2 α ) = B H A H = 108 x \tan(2\alpha)=\dfrac{BH}{AH}=\dfrac{108}{x} tan ( 2 α ) = A H B H = x 108
tan ( 2 α ) = 2 tan ( α ) 1 − tan 2 ( α ) = 108 x \tan(2\alpha)=\dfrac{2\tan(\alpha)}{1-\tan^2(\alpha)}=\dfrac{108}{x} tan ( 2 α ) = 1 − tan 2 ( α ) 2 tan ( α ) = x 108
108 x = 2 ⋅ 36 x 1 − ( 36 x ) 2 \dfrac{108}{x}=\dfrac{2\cdot\dfrac{36}{x}}{1-(\dfrac{36}{x})^2 } x 108 = 1 − ( x 36 ) 2 2 ⋅ x 36 1 − ( 36 x ) 2 = 2 3 1-(\dfrac{36}{x})^2=\dfrac{2}{3} 1 − ( x 36 ) 2 = 3 2
x = 36 3 x=36\sqrt{3} x = 36 3
α = 30 ° \alpha=30\degree α = 30° The right triangle Q C H QCH QC H
Let C H = y , ∠ Q C H = β . CH=y, \angle QCH=\beta. C H = y , ∠ QC H = β . Then tan ( β ) = Q H C H = 53.5 y \tan(\beta)=\dfrac{QH}{CH}=\dfrac{53.5}{y} tan ( β ) = C H Q H = y 53.5
The right triangle B C H BCH BC H
tan ( 2 β ) = B H C H = 108 y \tan(2\beta)=\dfrac{BH}{CH}=\dfrac{108}{y} tan ( 2 β ) = C H B H = y 108
tan ( 2 β ) = 2 tan ( β ) 1 − tan 2 ( β ) = 108 y \tan(2\beta)=\dfrac{2\tan(\beta)}{1-\tan^2(\beta)}=\dfrac{108}{y} tan ( 2 β ) = 1 − tan 2 ( β ) 2 tan ( β ) = y 108
108 y = 2 ⋅ 53.5 y 1 − ( 53.5 y ) 2 \dfrac{108}{y}=\dfrac{2\cdot\dfrac{53.5}{y}}{1-(\dfrac{53.5}{y})^2 } y 108 = 1 − ( y 53.5 ) 2 2 ⋅ y 53.5 1 − ( 53.5 y ) 2 = 107 108 1-(\dfrac{53.5}{y})^2=\dfrac{107}{108} 1 − ( y 53.5 ) 2 = 108 107
( y 53.5 ) 2 = 108 (\dfrac{y}{53.5})^2=108 ( 53.5 y ) 2 = 108
y = 321 3 y=321\sqrt{3} y = 321 3 Then
A C = A H + C H = 36 3 + 321 3 = 357 3 AC=AH+CH=36\sqrt{3}+321\sqrt{3}=357\sqrt{3} A C = A H + C H = 36 3 + 321 3 = 357 3
S A B C = 1 2 B H ⋅ A C = S_{ABC}=\dfrac{1}{2}BH\cdot AC= S A BC = 2 1 B H ⋅ A C =
= 1 2 ( 108 ) ( 357 3 ) = 19278 3 =\dfrac{1}{2}(108)(357\sqrt{3})=19278\sqrt{3} = 2 1 ( 108 ) ( 357 3 ) = 19278 3
S 3 = 57834 S\sqrt{3}=57834 S 3 = 57834
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