Trig identities

Trigonometry equalities, inequalities and expressions - sin, cos, tan, cot

Trig identities

Postby ken_165 » Wed Aug 22, 2018 4:59 am

I have a question...
The question says: tan2x=2tanx/1-tan^2x.
How did it become 2tanx and 1-tan^2x?
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Re: Trig identities

Postby nathi123 » Wed Aug 22, 2018 6:47 am

[tex]tg2x=tg(x+x)=\frac{tgx+tgx}{1-tgx.tgx}=\frac{2tgx}{1-tg^{2}x}[/tex]
[tex]tg (\alpha + \beta ) = \frac{tg\alpha+tg\beta}{1-tg\alpha.tg\beta}[/tex] if [tex]\alpha = \beta = x[/tex].

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