In the figure given below, measures of some angles are indicated. Find the value of x.
Answers
Answer:
Given: ∠DAE=30
∘
,DFC=60
∘
,∠FEG=120
∘
To find: ∠FCH=x
∘
Solution: Clearly, ∠AED+∠FEG=180
∘
[Linear pair]
⇒∠AED+120
∘
=180
∘
⇒∠AED=180
∘
−120
∘
⇒∠AED=60
∘
Now, △AED by angle sum property of triangle, we have
∠ADE+∠AED+∠DAE=180
∘
⇒∠ADE+60
∘
+30
∘
=180
∘
⇒∠ADE=180
∘
−60
∘
−30
∘
⇒∠ADE=90
∘
Again clearly, ∠ADE+∠FDC=180
∘
[Linear pair]
⇒90
∘
+∠FDC=180
∘
⇒∠FDC=180
∘
−90
∘
⇒∠FDC=90
∘
Again, in △FDC by angle sum property of triangle, we have
∠FDC+∠DFC+∠FCD=180
∘
⇒90
∘
+60
∘
+∠FCD=180
∘
⇒∠FCD=180
∘
−90
∘
−60
∘
⇒∠FCD=30
∘
Again clearly, ∠FCD+∠FCH=180
∘
[Linear pair]
⇒30
∘
+∠FCH=180
∘
⇒∠FCH=180
∘
−30
∘
⇒∠FCH=150
∘
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ANSWER: 150
STEP-BY-STEP EXPLANTION:
∠DEA = 180° - 120° = 60° (Angle sum property of a triangle)
∠DAE = 30°
In triangle DAE,
∠DAE + ∠DEA + ∠ADE = 180° (Angle sum property of a triangle)
60° + 30° + ∠ADE = 180°
∠ADE = 90°
∠CDF = 180° - ∠ADE (linear pair)
∠CDF = 180° - 90° = 90°
∠CDF = 90°
In triangle CDF,
∠CDF + ∠DFC + ∠DCF = 180°
90° + 60° + ∠DCF = 180°
∠DCF = 180° - 150°
∠DCF = 30°
∠x + ∠DCF = 180° (linear pair)
∠x = 180° - 30°
∠x = 150°