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Trigonometric functions

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Find the value of Sec A. and I have a right triangle BC=30 and BA=34
A)17/8
B)9/17
C)15/17
D)17/15
I chose D

  • Trigonometric functions -

    There is missing data here. Is 30 the hypotenuse or one of the legs of the right triangle? The same for 34. There is no way for me to know if BC is one the legs or is BA is the hypotenuse or vice-versa.

    Once I know that, I can proceed to help you.

  • Trigonometric functions -

    BA is the hypotenuse
    BC is the opposite leg

  • Trigonometric functions -

    We use the Pythagorean Theorem to find length AC as step 1. In other words, we MUST find the ADJACENT LEG.

    AC^2 + BC^2 = BA^2

    AC^2 + (30)^2 = (34)^2

    AC^2 900 = 1156

    AC^2 = 1156 - 900

    AC^2 = 256

    We now take the square root of both sides of the equation to find AC.

    sqrt{AC^2} = sqrt{256}

    AC = 16

    We now have all three sides.

    We need secant.

    What is secant?

    Secant = hypotenuse/adjacent

    Well, 34 is our hypotenuse and we just found AC (our adjacent). See it?

    Secant = 34/16

    The improper fraction 34/16 = 2_1/8 as a mixed number when reduced to the lowest term.

    However, 2_1/8 written as an improper fraction is 17/8.

    Final Answer: Choice (A)

    Done!

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