A) \[50{}^\circ \]
B) \[80{}^\circ \]
C) \[40{}^\circ \]
D) \[60{}^\circ \]
Correct Answer: B
Solution :
[b] in \[\Delta \,ABC,\] \[\angle \,A+\frac{1}{2}\angle \,B+\angle \,C=140{}^\circ \] (i) [given] But in \[\Delta \,ABC\] \[\Delta \,A+\angle \,B+\angle \,C=180\] (i) Subtract Eq. (i) from Eq. (ii), we get \[\frac{1}{2}\angle B=40\]\[\Rightarrow \]\[\angle \,B=40\times =80{}^\circ \] |
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