SEARCH HOME
 Math Central Quandaries & Queries
 Question from Yamama: hello ! I need help to solve this equation : 2cos^2 x + sin x = 2 Thank you very much Regards

Hi Yamama,

Write the equation as

$2cos^2 x + sin x -2 = 0$

and use the fact that

$\sin^2(x) + \cos^2(x) = 1$

to express your equation as a quadratic in $\sin(x).$ Solve the quadratic.

If you have an app on your computer that will graph equations you can use it to plot the graph of

$y = 2cos^2 x + sin x -2$

to verify that you have found all the solutions.

Penny