7th Class Mathematics The Triangle and its Properties

  • question_answer 5)
    Find the value of the unknown interior angle \[x\] in the following figures: (i)                                             (ii) (iii)                                              (iv) (v)                                                 (vi)                

    Answer:

                    (i)            \[{{115}^{o}}=\text{ }x\text{ }+{{50}^{o}}\]                                    \[\left| \begin{align}   & \text{The exterior angle of a triangle i equal to} \\  & \text{the um of it two interior oppoite angle} \\ \end{align} \right.\] \[\Rightarrow \]               \[x={{115}^{o}}-{{50}^{o}}\] \[\Rightarrow \]               \[x={{65}^{o}}\] (ii)           \[{{100}^{o}}=x+{{70}^{o}}\]                \[\left| \begin{align}   & \text{The exterior angle of a triangle is equal to} \\  & \text{the sum of its two interior opposite angles} \\ \end{align} \right.\] \[\Rightarrow \]               \[x={{100}^{o}}-{{70}^{o}}\] \[x={{30}^{o}}\] (iii)          \[{{125}^{o}}=\text{ }x+90\]°                 \[\left| \begin{align}   & \text{The exterior angle of a triangle is equal to} \\  & \text{the sum of its two interior opposite angles} \\ \end{align} \right.\] \[\Rightarrow \]               \[x={{125}^{o}}-{{90}^{o}}\]                 \[\Rightarrow \]               \[x={{35}^{o}}\] (iv)         \[{{120}^{o}}=x+{{60}^{o}}\]                \[\left| \begin{align}   & \text{The exterior angle of a triangle is equal to} \\  & \text{the sum of its two interior opposite angles} \\ \end{align} \right.\] \[\Rightarrow \]               \[x={{120}^{o}}-{{60}^{o}}\]                 \[\Rightarrow \]               \[x={{60}^{o}}\] (v)          \[{{80}^{o}}=x+{{30}^{o}}\] \[\left| \begin{align}   & \text{The exterior angle of a triangle is equal to} \\  & \text{the sum of its two interior opposite angles} \\ \end{align} \right.\] \[\Rightarrow \]               \[x={{80}^{o}}-{{30}^{o}}\]                 \[\Rightarrow \]               \[x={{50}^{o}}\]  (vi)        \[{{75}^{o}}=x+{{35}^{o}}\]                \[\left| \begin{align}   & \text{The exterior angle of a triangle is equal to} \\  & \text{the sum of its two interior opposite angles} \\ \end{align} \right.\] \[\Rightarrow \]               \[x={{75}^{o}}-{{35}^{^{o}}}\]                 \[\Rightarrow \]               \[x={{40}^{o}}\]


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