A) Equilateral
B) Right angled
C) Isosceles
D) None of these
Correct Answer: B
Solution :
It is obvious. Trick: Obviously it is not an equilateral triangle because A=B=C=60o does not satisfy the given condition. But B = 90o then \[{{\sin }^{2}}B=1\] and \[{{\cos }^{2}}A+{{\cos }^{2}}C={{\cos }^{2}}A+{{\cos }^{2}}\left( \frac{\pi }{2}-A \right)\,\] \[=\,{{\cos }^{2}}A+{{\sin }^{2}}A=1\] Hence this satisfy the condition, so it is a right angle triangle but not necessarily isosceles.
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