Question

Find the angle θ if 0 < θ < 90°:
cos 20 = sin θ​

Answer 1

$\bold{ANSWER≈}$

Let me take theta as A (just because it will be inconvenient to write theta on move version )

Sin(90+A)

So

Sin(A+B)= sinA cosB+ cosA sinB

Here we take B=90

Sin(A+90)= sinA cos90+ sin90cosA

= CosA

Hence sin(90+A)=cos A….

Hope this helps…