| arc sin x + arc sin y = | arc sin x – arc sin y = |
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| arc cos x + arc cos y = | arc cos x – arc cos y = |
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| arc tan x + arc tan y = | arc tan x – arc tan y = |
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| 2 arc sin x = | 2 arc cos x = |
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| 2 arc tanx = | cos (n arc cos x) = |
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