Postsecondary • 4mo.

Hello,

I don’t really understand what we should do in this question to find the answers can you explain this to me please?

Thank you in advance!

Français

Postsecondary • 4mo.

Hello,

I don’t really understand what we should do in this question to find the answers can you explain this to me please?

Thank you in advance!

Explanation from Alloprof

This Explanation was submitted by a member of the Alloprof team.

Thank you for your question!

For the two first questions, I recommend that you use some of the identities for cos(2t) and sin(2t). For example :

$$ cos(2t) = 2cos^2t-1 $$

$$ cos(2t) = 1 - 2sin^2t $$

$$ sin(2t) = 2sin(t)cos(t) $$

For the second part (with t/2), I recommend that you use the same formulas as above, but as

equations. Specifically, you can consider cos(t) to be equivalent to cos(2•t/2), therefore, for example :$$ -\frac{7}{9} = 2cos^2(\frac{t}{2})-1 $$

Don't hesitate to ask for more help if you need it!