Periodomania.

Algebra Level 4

Find the fundamental period of the function:

f ( x ) = s i n x + c o s x f(x)=|sinx|+|cosx|


  • Try this Problem no one has solved it till now ,maybe its hard.


The answer is 1.5708.

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2 solutions

Karan Shekhawat
Apr 17, 2015

ohh my god .... I don't believe I got 225 Point's for this atmost Level-2 , Problem.......

Peace-peace!

Gautam Sharma - 6 years, 1 month ago
Curtis Clement
Apr 17, 2015

Method 1: If you draw both |sin(x)| and |cosx| separately you will see that the modulus function flips the negative part of the curve, such that each curve has a period of π \pi . Now both curves are symmetrical and periodic, but they are in antiphase so the period of |sinx| + |cosx| is π 2 \frac{\pi}{2}

Method 2 (probably the better one): Draw a unit circles and cut off the bottom part. If you pick a point of the semicircle at angle x and drop a perpendicular line to form a right-angled triangle, then the adjacent side is equal to cos(x) and the opposite will be equal to sin(x). Now the only quadrant that satisfies both sin(x) > 0 and cos(x) > 0 is the top-right quadrant. Therefore the period is π 2 \frac{\pi}{2} .

Feel free to ask for clarification :)

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