A-Level Maths: E8-01 Proving Trigonometric Identities: The Methods

[harrysmith]

So it is invalid to rearrange the conjecture statement and prove the rearranged form is true?

[manomaylr]

With the “moving things across the equals sign” couldn’t it be done as a “reverse proof by contradiction” where you assume that they are equal and then prove that there is no contradiction