I have a test tomrow and i cant do some of the problems on the topic please help. i want to know how to do these before my test tomrow
express sin 320degrees as a sin function of a positive acute angle
find the value of cos^2 x - 2cos x= 0
thx
I have a test tomrow and i cant do some of the problems on the topic please help. i want to know how to do these before my test tomrow
express sin 320degrees as a sin function of a positive acute angle
find the value of cos^2 x - 2cos x= 0
thx
$\displaystyle \sin(320) = -\sin(40)$
320 degrees is 40 degrees below the (+) x-axis
$\displaystyle \cos^2{x} - 2\cos{x}= 0$
factor out $\displaystyle \cos{x}$ ...
$\displaystyle \cos{x}(\cos{x} - 2) = 0$
$\displaystyle \cos{x} = 0$ at $\displaystyle x = \frac{\pi}{2}$ and $\displaystyle x = \frac{3\pi}{2}$
$\displaystyle \cos{x} = 2$ has no solution.