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If 5*sin x = 5*cos x, what is x?

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jvt510 | Student, Undergraduate | eNotes Newbie

Posted July 30, 2011 at 7:50 AM via web

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If 5*sin x = 5*cos x, what is x?

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shaznl1 | High School Teacher | Salutatorian

Posted July 30, 2011 at 10:10 AM (Answer #1)

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let theta = x

The whole equation becomes

5 sin x = 5 cos x

divide both sides by 5

we get

sin x = cos x

if the answer is in radians

then since sin x =  cos (pi/2 - x)

then the equation becomes

cos (pi/2-x) = cos x

pi/2 - x = x

x= pi/4

of course, since cos and sin are like waves, this equation have multiple answers

sin and cos rotate in a cycle of  2pi

and sin and cos grphs meet two times per cycle

the general theta answer = pi/4 + kpi

k is a whole number constant

for degree answers, it is 45 + k180

k is a whole number constant

hope this helps

 

 

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted August 3, 2011 at 9:49 PM (Answer #2)

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We have to find x given that 5*sin x = 5*cos x

5*sin x = 5*cos x

=> sin x = cos x

=> sin x / cos x = 1

=> tan x = 1

=> x = arc tan (1)

=> x = 45 degrees

As the tan function is periodic with a periodicity of 180 degrees, x = 45 + n*180 degrees

The value of x is 45 + n*180 degrees.

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