1. ## Trigonometric identites

Hey this question above.

my working out

tan theta= 1/cot theta = cos theta/ sin theta
tan theta= cos ( -7/24) / sin(-7/24)

cos theta=0.957766
sin theta= -0.287549 or 0.29

the back of the book says
cos theta - 24/25, thats correct
but sin theta=-7/25 which equals -0.28

help?

thanks

2. And this

my working out 1 + tan^2theta = sec^2theta
squareroot 1.16 = sec theta
sec theta= 1.07703

how do i find when its neg of pos?

thank you again

3. Originally Posted by smmmc
Hey this question above.

my working out

tan theta= 1/cot theta = cos theta/ sin theta
tan theta= cos ( -7/24) / sin(-7/24)

cos theta=0.957766
sin theta= -0.287549 or 0.29

the back of the book says
cos theta - 24/25, thats correct
but sin theta=-7/25 which equals -0.28

help?

thanks
$\displaystyle \tan{\theta} = -\frac{7}{24} = \frac{opposite}{adjacent}$

sketch a reference triangle in quad IV ... hypotenuse = 25

$\displaystyle \sin{\theta} = \frac{opposite}{hypotenuse} = -\frac{7}{25}$

$\displaystyle \cos{\theta} = \frac{adjacent}{hypotenuse} = \frac{24}{25}$

4. Originally Posted by smmmc
And this

my working out 1 + tan^2theta = sec^2theta
squareroot 1.16 = sec theta
sec theta= 1.07703

how do i find when its neg of pos?

thank you again
$\displaystyle \tan{\theta} = 0.4 > 0$ ... \theta is in quad III, so $\displaystyle \sec{\theta} < 0$

$\displaystyle \sec{\theta} = -\sqrt{1 + \tan^2{\theta}}$