Ans. my question and read it carefully pls need a reliable ans.
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No this is not true that we must take thetha = 90
put any value of thetha you will get answer equal to 1
ex put thetha = 30
--- > 1/4+3/4 = 1
krishnagupta41:
the theta taken is the fixed angle and the angle is only one angle as in sintheta and costheta
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well you got it all wrong. it is one and Only one 90° angle in a right angle triangle. even if we write cos^2 theta + sin^2 theta = 1, it is still one angle namely theta. and the formula above is valid for all angle theta and not Only 90°. 90° is just a special case and to prove the formula we do not take theta = 90° because it would not be a proof. when we talk proof it is usually about the general case and not the special one.
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