standard_description: Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by finding the number that makes 10 when added to 8.
problem_activity: Problem 1
Prove the cofunction identity of:
$${\mathrm{cos}\left({\pi\over2}-x\right)=\mathrm{sin}x}$$
Using the sum or difference formula.
Problem 2
Solve:
$${\mathrm{sin}\left(x+{\pi\over4}\right)+1=\mathrm{sin}\left({\pi\over4}-x\right)}$$
for
$${0 \leq x \leq 2\pi}$$
.


aligns: no