Question 933905: Hello. My name is Jonny. I am a fifth year pupil attending an academy located in Scotland. Currently, I am struggling with one of the questions presented in my school-issued copy of Heinemann Mathematics (second edition). The question [7] appears in exercise 11J and is worded as follows:
"The diagram shows two telegraph poles, AB and ED, with support wires pegged at a single point C. Find the exact value of a) cos ACB; b) sin ECD; c) cos ACE; d) sin ACE"
The diagram shows two right-angled triangles (one [ABC], and another [ECD]), facing one another, intersect at point C on a straight horizontal line. Furthermore, the left-most triangle exhibits lengths of AB [opposite] (6m) and BC [adjacent] (10m). The right-most triangle exhibits lengths ED [opposite] (5m) and CD [adjacent] (3m).
I have successfully tackled parts "a" and "b" - with both answers coming to (5/√ 34). However, I cannot understand how to solve "c", and subsequently, "d".
Any assistance on answering the question would be very much appreciated. Thank you for taking the time to read and consider my enquiry.
Additional information: The question/exercise is an element of the double-angle/addition formulae section, in regards to trigonometry.
Answer by MathLover1(20850)   (Show Source):
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