Find the exact value of each expression, leaving your answer in surd form where necessary: (a) cos 40° cos 50° – sin 40° sin 50° (b) sin 37° cos 7° – cos 37° sin 7° i wish to know how we find the values of non special trigonometric angles like 15 , 25 ,1 7 like dat?

we have three similar triangles, because each has a right angle and shares an angle.   let's write the angles in order: opposite to short leg, long leg, hypotenuse.

cab similar to bad similar to cbd

or as ratios,

ca: ab: cb = ba: ad: bd = cb: bd: cd

we also know

ac = ad + cd

(ad+cd): ab: cb = ba: ad: bd = cb: bd: cd

(ad+cd)/cb=cb/cd

we have cb=6, ad=5 and seek x=cd.

we reject the negative root and conclude x=4

answer: 4

step-by-step explanation:

where is the question is there is a formula or is there not one

first the equation needs to be simplified. so the equation would now look like:   52-24+11

then you multiply.

and when you multiply, you will get the answer of 39.  

the linear relationship that represents a variation in direct proportion is the linear function that varies according to the numbers of its domain, for example the cost of producing x number of items can be represented in direct proportion by f (x) = mx + b, where m is the constant of proportionality, x the number of articles produced and b the fixed cost