## anonymous 3 years ago could anyone help me with the half angle formulas for tan. i have tan(5pi)/4 i can get everything plugged into the formula but i am having trouble simplify @precal

• This Question is Open
1. ajprincess

Do u want to find the value of tan(5pi)/4?

2. ajprincess

@bfinn4

3. anonymous

yes the exact value

4. anonymous

i am having trouble simplify all the radical stuff..and i dont have a way to type a radical into this web site so i dont know how to show you my work?

5. anonymous

oops i typed that woring i want the value of tan(5pi)/8

6. anonymous

or tan [((5pi)/4)/2]

7. ajprincess

$$sqrt{}$$ u can use this to type radicals.

8. ajprincess

$\tan\theta=\frac{2tan(\frac{\theta}{2})}{1-tan^2(\frac{\theta}{2})}$

9. ajprincess

$\frac{\theta}{2}=\frac{5\pi}{8}$ $\theta=\frac{5\pi}{4}$ plugging this in the formula gives u $\tan\frac{5\pi}{4}=\frac{2tan\frac{5\pi}{8}}{1-tan^2\frac{5\pi}{8}}$ $\pi=180$ so $\frac{5\pi}{4}=225$ do u knw the value of tan225?

10. anonymous

1

11. ajprincess

yup good:)

12. ajprincess

so $\tan\frac{5\pi}{4}=1$. $1=\frac{2tan\frac{5\pi}{8}}{1-tan^2\frac{5\pi}{8}}$ Let us assume $x=\tan\frac{5\pi}{8}$ $1=\frac{2x}{1-x^2}$ $1-x^2=2x$ $x^2+2x-1=0$ Can u find x?

13. ajprincess

@bfinn4

14. anonymous

i have to go to class but yes i can find x ...i will do it right after geology.

15. ajprincess

k 5n:)

16. precal

@ajprincess she did a great job helping you