Question

find the value of sin²31+cos²69​

Answer 1

Step-by-step explanation:

The above identity is the very reason why the two functions are called ‘sine’ and ‘COsine’ . Highlighted the ‘CO’ over here because this ‘CO’ stands for ‘Complementary’. Or in other words if you put some input x in the function sinx then cosx will give you the same output for the complementary input 90−x .

sin2x+cos2x=1 ..(2)

Now you see,

sin70=cos(90−70)=cos20 by (1)

Hence, sin270+sin220=cos220+sin220=1 by (2)

Hence the answer is 1 .