Question

Keisha and David each found the same value for cosine theta, as shown below, given Sine theta = Negative StartFraction 8 Over 17 EndFraction. Keisha’s Solution David’s Solution Tangent squared theta + 1 = secant squared theta. StartFraction sine squared theta Over cosine squared theta EndFraction + 1 = StartFraction 1 Over cosine squared theta EndFraction. StartFraction (eight-seventeenths) squared Over cosine squared theta EndFraction + 1 = StartFraction 1 Over cosine squared theta EndFraction. (eight-seventeenths) squared + cosine squared theta = 1. cosine theta = plus-or-minus StartRoot 1 minus StartFraction 64 Over 289 EndFraction EndRoot. cosine theta = plus-or-minus Fifteen-seventeenths sine squared theta + cosine squared theta = 1. cosine squared theta = 1 minus (negative eight-seventeenths) squared. cosine theta = plus-or-minus StartRoot StartFraction 225 Over 289 EndFraction EndRoot. Cosine theta = plus-or-minus fifteen-seventeenths Whose procedure is correct? Keisha’s procedure is correct. David’s procedure is correct. Both procedures are correct. Neither procedure is correct.

Answer 1

c) both are correct

Explanation:

Answer 2

C) Both procedures are correct

Explanation:

1 + tan²(theta) = sec²(theta)

And

cos²(theta) = 1 - sin²(theta)

Are both valid identities