Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**Zzulu****Guest**

I'll try to translate these questions to the best of my ability, since it's originally written in Swedish. (there's a distinct lack of online math discussion over here for some reason) I have 2 questions in total.

Here it goes;

1- I have to calculate the exact value of sin(105). How do I do that?

2- I need to calculate the "area" between these two f(t)=13t-5t^2 and f(t)= 1/2t

All help is appreciated!

**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 21,467

Zzulu,

I shall help you with the first problem.

Sin(A+B)=SinACosB+CosASinB

Sin(105)=Sin(60+45)=Sin60Cos45+Cos60Sin45

We know, sin60=√3/2, cos45=1/√2, cos60=1/2, sin45=1/√2

Therefore, Sin(105)=√3/2√2+1/2√2= (√3+1)/2√2

= (approximately) 0.9659

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

**Online**