## Algebra and Trigonometry 10th Edition

$(sin~x+cos~x)^2=1+2~sin~x~cos~x$
Remember that: $sin^2x+cos^2x=1$ $(sin~x+cos~x)^2=sin^2x+2(sin~x)(cos~x)+cos^2x=(sin^2x+cos^2x)+2~sin~x~cos~x=1+2~sin~x~cos~x$