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| 1. |
Prove 2tanx - cotx = -1 |
| Answer» 2tan x - cot x + 1 = 02tan x - 1/tan x + 1 = 02tan2x - 1 + tan x = 02tan2x + tan x - 1 = 02tan2x + 2tan x - tan x - 1 = 02tan x(tan x + 1) - 1 (tan x + 1) = 0(tan x + 1)(2tan x - 1) = 0tan x + 1 = 0 or 2tan x - 1 = 0tan x = -1 or tan x = 1/2x = 3π/4, 7π/4 or x = 3.6052, 0.4636 | |