lim x-> 7pi/4 (cosx+sinx)/(cos2x)(adsbygoogle = window.adsbygoogle || []).push({});

so what i was trying to do here was replace cos2x with the double angle id which is cos^2x-sin^2x

then i factor that and cancle out cosx+sinx

now i have 1/cosx-sinx...so i tried direct sub. and i get 1/sqroot2/2+squroot2/2 which i end up with sqroot 2 but that isn't the right answer

isn't cos 7(pi/4)= squroot 2/2 and sin 7(pi/4)= -squroot2/2?

please show me where i am going wrong

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Trig limit

**Physics Forums | Science Articles, Homework Help, Discussion**