Hello,
I solved an exercise where it is necessary to prove the subtraction formula for cosine. The next exercise asks to prove addition formula for cosine using the formula in the previous exercise. So it is either asking for the subtraction formula or the formulas that I have used to prove the subtraction formula, I used distance formula and compared it with law of cosines to come up with subtraction formula. Not quite sure how I am supposed to prove the addition formula.
There is my proof for subtraction formula of cosine:
I am very sure that the solution is super easy, I simply cannot seem to think of it... Thank you.
I solved an exercise where it is necessary to prove the subtraction formula for cosine. The next exercise asks to prove addition formula for cosine using the formula in the previous exercise. So it is either asking for the subtraction formula or the formulas that I have used to prove the subtraction formula, I used distance formula and compared it with law of cosines to come up with subtraction formula. Not quite sure how I am supposed to prove the addition formula.
There is my proof for subtraction formula of cosine:
I am very sure that the solution is super easy, I simply cannot seem to think of it... Thank you.
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