We know how A’levels like to combine a few topics across. We also know how bad trigonometry can be. I was coaching my International Bachelorette (IB) class last week and came across a fairly interesting question. It tests students on their abilities to manage double angle identities. Not a tough question, but definitely good practice 🙂
FYI: All double angle identities are found in MF26.
Here it is…
(a) Show that , .
(i) Use the double angle identity to show that .
(ii) Show that .
(iii) Hence find the value of exactly.
Since , ,