Hello, LoveDeathCab!

. . . . - . . .sin xShow that the equation: .tan x .= .4·cos x

may be written as: .4·sin²x + sin x - 4 .= .0

We have: .------ .= .4·cos x

. . . . - . . .cos x

Multiply by cos x: .sin x .= .4·cos²x

Then we have: .sin x .= .4(1 - sin²x) . → . sin x .= .4 - 4·sin²x

Therefore: . 4·sin²x + sin x - 4 .= .0