Question

Answer fast maths in up board​

Answer 1

1. I have change sin 18 to sin(90-72)
2. as u know 90-72 is 18
3. in last one the ans came out as cos72/cos72 bcuz
4. we know that sin(90 - theta) is cos(theta)

• HOPE MY ANS HELP U

Answer 2

$\frac{ \sin(18) }{cos \: 72}$

= (sin(90°-72°))/cos72°

= cos 72°/cos 72°

=1

REMEMBER :

1) sin(90°-theta) = cos theta

2) cos(90°-theta) = sin theta

3) cot(90°-theta) = tan theta

4) tan(90°-theta) = cot theta

5) sec(90°-theta) = cos theta

6) cos(90°-theta) = sec theta