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Question:


lizbethortiz
Student
High School - 12th Grade

I need to verify the following identity:

secβ-cosβ = tanβsecβ

explain it step by step please ...

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Posted by lizbethortiz on Friday February 27, 2009 at 9:07 PM and tagged with identity, math, precalculus.

Answers:

  1. giorgiana1976
    giorgiana1976 Teacher
    Doctorate

    eNotes Editor

    The expression from the left side is not equal to the one on the right side.

    Let's demonstrate this:

    sec b = 1/cos b

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

    [1-cos^2(b)]=cosb*(sin b/cos b)(1/cos b)

    [1-cos^2(b)]= tg b

    sin^2(b) = tg b

    sin^2(b) = (sin b/cos b)

    sinb = 1/cos b

    sin b = sec b NOT TRUE!

    Rate answer:

    Posted by giorgiana1976 on Saturday February 28, 2009 at 12:32 PM