# Thread: Trig Help Please

1. ## Trig Help Please

This is something I've never really gotten the hang of...

If tan 20 = t ; how could the following be expressed in terms of t?

a) tan 70
b) tan 40
c) tan 200
d) sec 20

My answers:

a) $\frac{1}{t}$

b) $?$

c) $t$

d) $\sqrt{(t^2 + 1)}$

2. b) $\tan 2x=\frac{2\tan x}{1-\tan ^2x}$

$\tan 40=\frac{2\tan 20}{1-\tan ^220}=\frac{2t}{1-t^2}$

3. Hello, janvdl!

It looks like you've got the hang of it . . .

If $\tan 20 = t$, how could the following be expressed in terms of $t$?

$a)\;\tan 70\qquad b)\;\tan 40\qquad c)\;\tan 200\qquad d)\;\sec 20$

My answers:

$a)\; \frac{1}{t}\qquad b)\;? \qquad c)\;t \qquad d)\;\sqrt{t^2 + 1}$

For (b), use the Double-Angle Identity: . $\tan2\theta \:=\:\frac{2\tan\theta}{1 - \tan^2\theta}$

And your answers are correct . . . nice work!