Math

[tonykangus]

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Hi Members.
Can you help those questions?

1) Sin^2(150*) + Cos^2 (120*)=

 

[baedero1]

sin^2(150)=(1+cos300)/2
cos^2(120)=(1-cos240)/2

cos300 = 1/2
cos240 = -1/2

answer is 3/2

 

[Streetwolf]

Hi Members.
Can you help those questions?

1) Sin^2(150*) + Cos^2 (120*)=

It's just sin(150)*sin(150) + cos(120)*cos(120). No need for the extra formula there.

Just know that sin(150) = sin(5pi/6) and that cos(120) = cos(2pi/3). Then you know that sin(5pi/6) = 1/2 and cos(2pi/3) = -1/2.

So (1/2)^2 + (1/2)^2 = 1/4 + 1/4 = 1/2.

1/2 is the answer, not 3/2. I'm not sure what those equations are.

 

[tonykangus]

It's just sin(150)*sin(150) + cos(120)*cos(120). No need for the extra formula there.

Just know that sin(150) = sin(5pi/6) and that cos(120) = cos(2pi/3). Then you know that sin(5pi/6) = 1/2 and cos(2pi/3) = -1/2.

So (1/2)^2 + (1/2)^2 = 1/4 + 1/4 = 1/2.

1/2 is the answer, not 3/2. I'm not sure what those equations are.

I thank you for your help.