Asked by timithy
Evaluate the following with thought the use of a calculator:
Sin70.sin25 + sin65.sin20
And please people explain how you arrived in your answer
Lots of love, timmy
Sin70.sin25 + sin65.sin20
And please people explain how you arrived in your answer
Lots of love, timmy
Answers
Answered by
Steve
sin A sin B = ½ cos(A−B) − ½ cos(A+B)
sin70 sin25 = 1/2 [cos45 - cos95]
sin65 sin20 = 1/2 [cos45 - cos85]
sum to get
cos 45 - 1/2 [cos95 + cos85]
cos u + cos v = 2 cos(½(u+v)) cos(½(u−v))
cos95+cos85 = 2cos90 cos5
cos90=0, so we are left with
cos 45 = 1/√2
sin70 sin25 = 1/2 [cos45 - cos95]
sin65 sin20 = 1/2 [cos45 - cos85]
sum to get
cos 45 - 1/2 [cos95 + cos85]
cos u + cos v = 2 cos(½(u+v)) cos(½(u−v))
cos95+cos85 = 2cos90 cos5
cos90=0, so we are left with
cos 45 = 1/√2
There are no AI answers yet. The ability to request AI answers is coming soon!
Submit Your Answer
We prioritize human answers over AI answers.
If you are human, and you can answer this question, please submit your answer.