When to use complemtary angles for general solutions? (1 Viewer)

[rsingh]

Hey guys, I was just looking at the ways at doing trig eqts that ask for general solutions.

I've found that for some questions you can use complementary angles, however I'm not sure whether the general solutions for doing it that way are correct.

For example,

sin2x=cos x can be solved by doing 2sinxcosx - cosx=0
or alternatively,

sin 2x=sin(90-x) or cosx = cos (90-2x)

Can you do it the second way? Will the answers be correct? Because it will be a general solution different to that of the above.

Thanks.

 

[haboozin]

yea ofcourse u can use the second method... it will b correct and most importantly it will give you the same answer

but wouldn't it be like 10 times longer... ?


btw u double posted/