ATAR Notes: Forum

VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Specialist Mathematics => Topic started by: BubbleWrapMan on May 17, 2011, 10:08:38 pm

Title: Challenge - Trig Question
Post by: BubbleWrapMan on May 17, 2011, 10:08:38 pm: Simplify:

$\cos ^{2}108^{\circ}\cos ^{2}72^{\circ}+\sin ^{2}108^{\circ}\sin ^{2}72^{\circ}-\frac{1}{2}\sin 216^{\circ}\sin 144^{\circ}$

Just something I dreamt up.
Title: Re: Challenge - Trig Question
Post by: yawho on May 17, 2011, 10:24:53 pm: =(cos108cos72-sin108sin72)^2
=(cos(108+72))^2
=(cos180)^2
=1
Title: Re: Challenge - Trig Question
Post by: BubbleWrapMan on May 17, 2011, 10:39:58 pm: Good work, basically no one at my school can do it. D=
Title: Re: Challenge - Trig Question
Post by: soopertaco on May 29, 2011, 11:39:32 am: haha climb too high you amaze me :')