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Linear Approximation??????

sin 59

so far i got

sin 59 is about sin 60....

so (rad2/2)-dy is the equation

then you differenciate sinx

you get

dy=cos 60 dx

dx=x final- x initial

so dx= 60-59

dx=1

here is my issue if dx= 1

then plugging it back in dy=cos 60 (1)......dy=1/2

rad 2/2-.5=.207

and sin(59)=.6367

Ideas?

1 Answer

Relevance
  • kb
    Lv 7
    1 decade ago
    Favorite Answer

    The trigonometric formulas in Calculus work in radian measure nicely.

    59 degrees --> 59π/180 (radians).

    Note that π/3 (60 degrees) is close to 59π/180.

    So, let's find the linear approximation of y = sin x at x = π/3.

    Point: (π/3, √3/2).

    Slope: y' = cos x {at x = π/3} = 1/2.

    ==> y - √3/2 = (1/2)(x - π/3).

    So, the tangent line is y = √3/2 + (1/2)(x - π/3).

    For points near x = π/3, the tangent line will give a good approximation.

    So, sin x ≈ √3/2 + (1/2)(x - π/3).

    ==> sin(59π/180) ≈ √3/2 + (1/2)(59π/180 - π/3) ≈ 0.8573.

    I hope this helps!

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