Help here please:

Evaluate the following, give exact value when possible:
a. sec(225°):

Question

Help here please:

Evaluate the following, give exact value when possible:
a.	sec(225°):

anonymous · Answer

use the sum/difference rules:
225 = 180 + 45
-15 = 30 - 45

callisto · Answer

a.	sec(225°)
      = 1/cos225
      = 1/cos (180 +45)
      = 1/ -cos45
      = 1/(-sqrt2  /2)
      = 2/sqrt2
      = sqrt2

anonymous · Answer

Ok. One sec guys, Im going to try to solve the second one by myself

anonymous · Answer

mine was just a suggestion...you could also do 45-60 = -15 if you're more comfortable with that...

anonymous · Answer

Ok, so first its sin(30-45)=sin 30 cos45 - cos 30 sin 45

callisto · Answer

yes :)

anonymous · Answer

simplify....

anonymous · Answer

Then, its (1/2)(1/sqrt(2))-(sqrt(3)/2)(1/sqrt(2))

callisto · Answer

Yes, what's next?!

anonymous · Answer

then, its 1-sqrt(3) / 2sqrt(2)?

callisto · Answer

yes :)

anonymous · Answer

Is it by any chance = sqrt(2) - sqrt(6)/4?

callisto · Answer

yes, when you do the rationalisation

anonymous · Answer

so its correct right?

callisto · Answer

I think so, @dpaInc what do you think?

anonymous · Answer

great job!  :)

anonymous · Answer

Thanks @callisto, Thanks @dpainc, As usual you guys are awesome!

anonymous · Answer

Man, you guys teach so much better than my teachers :P!

anonymous · Answer

yw

anonymous · Answer

sin (75) would be sqrt(2) + sqrt(6)/4. right?

callisto · Answer

yes, according to my stupid calculator :P

anonymous · Answer

lol. Alright thank you:)

callisto · Answer

welcome :)