trig equa solve for x

Apr 2009
102
1
trig equa solve for x:

2(sinx)^2 + 7sinx-4=0

between 0 and 2pi.

How would yo go about doing this one>?
 
Nov 2009
717
133
Wahiawa, Hawaii
un FOIL

trig equa solve for x:

2(sinx)^2 + 7sinx-4=0

between 0 and 2pi.

How would yo go about doing this one>?
try to un FOIL it

\(\displaystyle (2sinx - 1)(sinx + 4) = 0\)

the rest is easy...

\(\displaystyle 2sinx = 1 \rightarrow sinx = \frac{1}{2} \rightarrow sin^{-1}\left(\frac{1}{2}\right) = \frac{\pi}{6}\ ,\frac{5\pi}{6}\)

\(\displaystyle sinx = -4\) is undefined.
 
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