Question

please answer the question​

Answer 1

Here's the Answer :

cos⁴ø - sin⁴ø = 1/2

=>( cos²ø)² - (sin²ø)² = 1/2

=>(cos²ø - sin²ø)(cos²ø + sin²ø)=1/2

=>( cos²ø - sin²ø )×1 = 1/2

=> cos²ø - sin²ø = 1/2

=> cos2ø = 1/2

=> cos 2ø = cos 60°

=> 2ø = 60°

=> ø = 30°