secis the abbreviation for second

tanis what one may get while visiting the beach

sinis a transgression

cosis the nickname of a famous black comedian

... in other words, a trig function without an argument means nothing.

now, if you meant ...

... then I recommend multiplying the left side of the equation by , then using the Pythagorean identity

now, can you be more clear with this equation ...

how would you verify 8sin^2cos^2=1-cos4?