# Thread: [SOLVED] Trigonometric help 2

1. ## [SOLVED] Trigonometric help 2

Use a calculator to find ,to four significant digits , approx. values of the other five trigonometric functions of theta:

a)cos theta=0.7816 and theta is in the first quadrant

How to do this question...
thank you

2. i think you would just find theta by using inverse cosine and then substitute it into the other five trignometric functions?

3. Originally Posted by hmmmm
i thibk you would just find theta and then substitute it into the other five trignometric functions?
how to subtitute it to find the value ?

4. Originally Posted by mj.alawami
Use a calculator to find ,to four significant digits , approx. values of the other five trigonometric functions of theta:

a)cos theta=0.7816 and theta is in the first quadrant

How to do this question...
thank you
Hello mj,

I showed you how to do this in the other post you neglected.

$\displaystyle \cos \theta=0.7816$

$\displaystyle \cos \theta = \frac{x}{r}=\frac{0.7816}{1}$

$\displaystyle \sec \theta = \frac{1}{0.7816}\approx 1.279$

Thus,$\displaystyle \boxed{r = 1}$ and $\displaystyle \boxed{x \approx 0.7816}$

Now find y.

$\displaystyle r^2=x^2+y^2$

$\displaystyle 1=(0.7816)^2+y^2$

$\displaystyle \boxed{y\approx 0.6238}$

Now you have x, y, and r. Go back to your other post and see the appropriate ratios so you can substitute these values in to find sin, tan, csc, and cot.