Question

Can anybody solve the question number seventh sum

Answer 1

LHS = sec⁴@ - cos⁴@

LHS = (sec²@)² - cos⁴@

LHS = (1-cos²@)² - cos⁴@

LHS = 1²+cos⁴@-2cos²@-cos⁴@

LHS = 1-2cos²@

LHS = RHS