Question

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Answer 1

\[\sin \left( 90-x \right)=\cos x,\cos \left( 90-x \right)=\sin x\]

Answer 2

The complement of the sine of an angle is represented by sin(x) = cos(90 - x). The reason why cosine is considered the complement of sine is because when you apply an any angle x to sine, its complement can be applied to the cosine and the result will be equal to sin(x). In case you forgot, two angles are complements of each other anytime the angles add to get 90 degrees. In other words

45 + 45 = 90

sin(45) = cos(45)

30 + 60 = 90
sin(30) = cos(60)

and so on and so forth.

Answer 3

You're welcome.