1)prove that tan x [(1+ sin x) / (1- cos x)] = cot x [(1+cos x ) /(1- sin x)]
2)tan^2 A +sec A =1 ,where -90度 <A<90度 , find the value tan A + sec^2 A.
trigonometric functions
2010-02-13 1:23 am
回答 (2)
2010-02-13 2:03 am
2010-02-13 5:27 am
tan^2A + secA= 1
sec^2A - 1 + secA - 1 = 0
sec^2A + secA - 2 = 0
(sec + 2)(secA - 1) = 0
sec A = 1 or sec A=-2 (rejected for -90 < A < 90)
sec A = 1 => A = 0 => tanA + sec^2 A = 1
sec^2A - 1 + secA - 1 = 0
sec^2A + secA - 2 = 0
(sec + 2)(secA - 1) = 0
sec A = 1 or sec A=-2 (rejected for -90 < A < 90)
sec A = 1 => A = 0 => tanA + sec^2 A = 1
收錄日期: 2021-04-23 23:23:47
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https://hk.answers.yahoo.com/question/index?qid=20100212000051KK01116