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Given sin A = 3/5, and 0° < A < 90°, find the values of cos A and tan A,?

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By using the formula: cos^2 A = 1 - sin^2 A and tan A = sin A / cos A
please explain in detail!
thanks.
asked May 4, 2013 in TRIGONOMETRY by futai Scholar

2 Answers

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sinA = 3 / 5 and 0 < A < pi / 2

Recall : Trigonometry identities sin2A + cos2A = 1 then cos2A = 1 - sin2A

Substitute sinA = 3 / 5 in the above formula

cos2A  = 1 - 9 / 25 = 16 / 25

cosA = 4 / 5  (First quadrant)

 

answered May 4, 2013 by diane Scholar
0 votes

sinA = 3 / 5 and 0 < A < pi / 2

Recall : Trigonometry identities sin2A + cos2A = 1 then cos2A = 1 - sin2A

Substitute sinA = 3 / 5 in the above formula

cos2A  = 1 - 9 / 25 = 16 / 25

cosA = 4 / 5  (First quadrant)

Recall : Trigonometry identities tanA = sinA / cosA

Substitute sinA = 3 / 5 and cosA = 4 / 5 in the above tanA formula

tanA = (3 / 5) / (4 / 5) = 3 / 4.

answered May 4, 2013 by diane Scholar

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