Jawabanmu

2014-03-20T22:13:44+07:00
cos 135 + cos 75cos (90 + 45) + cos (45 + 30 )[cos 90.cos 45 - sin 90.sin 45] + [cos 45.cos 30 - sin 45 .sin 30]
.....= [0.1/2
√2 - 1.1/2√2] + [1/2√2.1/2√3-1/2√2.1/2] .....= [0 - 1/2√2 +  [1/4√6 - 1/4√2
.....= -1/2√2 + 1/4√6-1/4√2
.....= 1/4
√6-1/2√2-1/4√2=1/4√6-1/2√2
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