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Dee W
Lv 7
Dee W asked in Science & MathematicsMathematics · 1 decade ago

Solve this trig identity. (secx - sinx)/cotx = cosx Thanks!?

2 Answers

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  • 1 decade ago
    Favorite Answer

    (secx - sinx) / cotx = cosx

    (1/cos(x) - sin(x)) / (cos(x) / sin(x)) = cosx

    1/cos(x) - sin(x) = cos(x)(cos(x) / sin(x))

    Multiply both sides by sin(x)

    sin(x)/cos(x) - sin(x)sin(x) = cos(x)cos(x)

    tan(x) - sin²(x) = cos²(x)

    tan(x) = cos²(x) + sin²(x)

    Remember from your Pythagorean trig identity that: cos²(x) + sin²(x) = 1

    Thus

    tan(x) = 1

    x = π/4, 3π/4, 9π/4, etc.

    Tip:

    Convert all sec(x), cot(x), etc into sin and cos forms.

    sec(x) = 1 / cos(x)

    cot(x) = cos(x)/sin(x)

    csc(x) = 1 / sin(x)

  • Anonymous
    5 years ago

    cosx(secx+cosxcsc^2x)---->remember that secx is only a million/cosx and cscx is only a million/csc^2x cosx (a million/cosx+cosx/sin^2x)-------->now distribute the cosx cosx/cosx+cos^2x/sin^2x----->cosx/cosx is only a million a million+(cos^2x/sin^2x)-------->now a million is likewise an identical as sin^2x/sin^2x ---->you are able to also comprehend that cos^2x/sin^2x=cot^2x and a million+cot^2x=csc^2x sin^2x/sin^2x+cos^2x/sin^2x------>you are able to now combine the numerators because now you've person-friendly denominators (sin^2x+cos^2x)/sin^2x----------->now remember that sin^2x+cos^2x is only a million a million/sin^2x---------->by using definition a million/sin^2x=csc^2x csc^2x

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