Let sin x be the answer to this question. Find the value of cos x .
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Simple standard approach.
@Pi Han Goh LOL , nice way of asking!
sin x = cos x ⇒ tan x = 1 ⇒ sec x = 1 2 + 1 = ± 2 ⇒ cos x = ± 2 1
O R
sin 2 x + cos 2 x = 1 ⇒ 2 cos 2 x = 1 ⇒ cos 2 x = 2 1 ⇒ cos x = ± 2 1
(Liked) This should be a logic question. Nice one!
Haha, why it should be in logic?
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I did spend some time comprehend the question... I think this is something called 'self-reference'?
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Yes, it's self-reference. But it's only in Logic if we want to decipher whether the statement is true or not. (See truth-tellers and liars )
Glad you liked this question! +1
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@Pi Han Goh – Oic. A logic question with a geometry coat =D
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@Pi Han Goh – Same method...done ;)
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@展豪 張 –
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@Pi Han Goh – Santi santi cazorla
@Pi Han Goh – Haha who's this guy?
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@展豪 張 – Haha no idea. I don't follow the football news.
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@Pi Han Goh – Neither do I... I have just created this , inspired by your problem. Try it ;)
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@展豪 張 – You should try converting it to MCQ (that is, delete your question unfortunately, then post another one). Plus, replace "statement" with "person". Then the description will be more fluid!
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@Pi Han Goh – You're right. A 'lying statement' just sounds weird...
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@展豪 張 – Hahah! no problem. When I first started posting logic problems, I didn't know how to phrase my questions as well....
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@Pi Han Goh – I face the same problem when I am posting solutions too. English is not my mother language....
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@展豪 張 – Haha! In my country, everyone speaks broken English!
@Pi Han Goh – He plays for Arsenal
sin x = cos x : if : x = 45 , so : sin ( - 45 ) = - sin 45 , cos ( - 45 ) = cos 45 .
Dude it was a good one. Good question
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Since answer to this question is unique and we have to find cos x when answer is sin x . Therefore this is posible only when both are same: sin x = cos x 1 = sin 2 x + cos 2 x = 2 sin 2 x = 2 cos 2 x ⟹ sin x = cos x = ± 2 1