Trigonomic Identities (1 Viewer)

[imoO]

Hey everybody, I have a question I came across while revising for my examsx...I'm in year 11...

I know how to do most of them like sin75 > sin(45+30) blah blah...

but where would I go from tan 285?...I think somehow it becomes tan 75 from 360-287...but I don't know. We've had a sub for alot of our classes and alot of things aren't cleared up.

reguards
imoO

 

[tommykins]

With your regions, 285 is in the fourth region, since its tan, it will be negative.

Thus, tan(285) becomes tan(-75) which then becomes -tan(75) = -tan(45+30)

 

[imoO]

thanks, I have another question tho...

sin (x+30) + cos (45+y)

do i expand them individually and then find exact values?...i leave sin x cos x etc...as they are...right?

 

[vds700]

yeah to simplify that i guess u would just expand them...

sin(x+30) + cos(45+y)
=sinxcos30 + cosxsin30 + cos45cosy -sin45siny
=sinx(sqrt3/2) + (1/2) cosx + (1/sqrt2)cosy - (1/sqrt2)siny

 

[imoO]

thanks for that