Question

prove this as fastly as you can

Answer 1

So simple
only formula based q.
please select as brain list answer
After third line
Tan²(theta) +1= Sec²(theta)
In 5th line Change
Sec²(theta)•[1+Tan²(theta)]/Tan²(theta)
Into
1/[Cos⁴(theta)•Sin²(theta)/Cos²(theta)]
AFter cut Cos²(theta)
Change left
Cos²(theta)
into
1-Sin²(theta)