Isn't it necessary to to have an 90 degree angle to solve any kind of trig problem?

First of all, an will not before 90°.

Yes it's necessary to have 90° as one of the angle in the triangle of which we are solving Trigonometry.

Even if it is not given, we have to make one angle any how by experimenting on other measurements of the triangle.

Hope this will help you. 

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the required function is .

step-by-step explanation:

from the given table it is noticed that the graph passing through (-3,7), (0,4), (3,1) and (8,-4).

it is a linear function because the value of y is decrease by one as the value of x increase by 1.

the slope of the function is

the slope of the function is -1 and the y-intercept is 4.

the slope intercept form is

where, m is slope and b is y-intercept.

therefore the required function is . the graph of this function is shown below.

step-by-step explanation: