[Toán 11] Phương trình lượng giác

N

nguyenbahiep1

[laTEX]dk: sin 2x \not = 0 \\ \\ sin x + cosx = \frac{cosx}{sin x} - \frac{sinx}{cosx} \\ \\ sin x + cosx = \frac{(cosx+sin x)(cosx -sinx)}{sin x.cosx} \\ \\ TH_1: sin x + cosx = 0 \Rightarrow tan x = - 1 \\ \\ sinx.cosx = cosx - sin x \\ \\ u = cosx - sinx \Rightarrow u^2 = 1 - 2sin x.cosx \\ \\ dk: | u | \leq \sqrt{2} \\ \\ u^2 + 2u - 1 = 0 [/laTEX]
 
L

lethilinht6

ban giai sai rui
cosx /sinx - sinx/cosx = cos2x/sinxcosx .
sau do ban quy dong => nhom => giai song
 
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