
William W. answered 02/28/22
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Math and science made easy - learn from a retired engineer
Using the identities:
1) sec(x) = 1/cos(x)
2) tan(x) = sin(x)/cos(x) therefore tan2(x) = sin2(x)/cos2(x)
3) sin2(x) + cos2(x) = 1 or sin2(x) = 1 - cos2(x)