Prove that

13

If cot θ = then prove that

14

Prove that 3(tan²30° + cot²30°) – 8(sin²45° + cos²30°) = 0

15

Prove that 4(sin⁴30° + cos60°) – 3(cos²45° – sin²90°) =

17

Prove that 2(cos²45° + tan²60°) – 6(sin²45° – tan²30°) = 6