help in trigonometry?

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If theta is an acute angle adn sin theta = 2/ square root of 7, use the identity sin squared theta + cos squared theta =1 to find cos.

2007-06-02 15:24:24 · 3 answers · asked by Nou Nou 1 in Science & Mathematics ➔ Mathematics

Let theta = x
sin x = 2 / √7
cos² x = 1 - sin²x
cos² x = 1 - 4/7
cos² x = 3 / 7
cos x = √(3/7) (in first quadrant)

2007-06-03 02:10:54 · answer #1 · answered by Como 7 · 0⤊ 0⤋

4/7 + cos^2 theta = 1
cos^2 theta = 3/7
cos theta = sqrt of (3/7)

2007-06-02 22:29:18 · answer #2 · answered by anggira dhita 2 · 0⤊ 0⤋

sin theta=2/sqrt7
being in the first quadrant cos theta will be positive
Therefore cos theta
=sqrt(1-sin^2theta)
=sqrt(1-4/7)
=sqrt(3/7)=sqrt3/sqrt7

2007-06-02 22:32:00 · answer #3 · answered by alpha 7 · 0⤊ 0⤋