SOLUTION: sin(90-x)=cosx why i dont under stand give me proof

Question 899010: sin(90-x)=cosx why i dont under stand give me proof
Found 2 solutions by rothauserc, Fombitz:
Answer by rothauserc(4718) (Show Source): You can put this solution on YOUR website!
Use trig identity
cos(a-b)=cos(a)*cos(b)+sin(a)*sin(b)
therefore,
cos(90-x)=cos(90)*cos(x)+sin(90)*sin(x...
cos90=0
sin90=1 ,,, --> cos(90-x)=sin(x)
another way to prove this is draw a right triangle
let angle A be 90 degrees, then
then angles B+C = 90 degrees and C = 90-B
cos(90-B) = b/a and sin B = b/a, therefore
cos(90-B) = sin B = b/a

Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!

Using this right triangle, by definition,

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