cos 30° = √3/2 ⇒ cos² 30° = 3/4

cos 60° = 1/2 ⇒ cos² 60° = 1/4

sec 30° = (1/cos 30°) = (2/√3) ⇒ sec² 30° = 4/3

tan 45° = 1 ⇒ tan² 45° = 1

sin 30° = 1/2 ⇒ sin² 30° = 1/4

We also know that sin² θ + cos² θ = 1

∴

= [(5×(1/4)) + (4×(4/3)) – (1)]/1

= (5/4) + (16/3) – 1

= (15 + 64 - 12)/12 = 67/12