2010 AMC 12B Problems/Problem 13
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We start by noticing that the maximum values for both the sine and the cosine function are 1.
Therefore, the only way for this equation to be true is if 
and 
, since if one of these equaled less than 1, the other one would have to be greater than 1 which contradicts our previous statement.
From this we easily conclude that 
and 
. Solving this system gives us 
and 
, which gives us a 
triangle. By drawing a diagram we can easily see that 
