Question 888539
A student is overheard saying :'i dont need to learn trig ratios . I am just going to use Sine and Cosine Laws to Solve problems. Show by example that the student is right. explain advantages and disadvantages to this approach.
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Bad idea!
While it is true you can derive all the remaining ratios from the sin and cos functions, you will be presented with problems that require a working knowledge of relationships between trig functions other than sin or cos. Take for example, the pythagorean identities: tan^2+1=sec^2 and cot^2+1=csc^2.
Some problems are difficult to solve without this knowledge. Also, the graphs of all trig ratios and their reciprocals look quite different from from each other. 
As I said, as student learning trig, its a bad idea to to think you only need to learn the sine and cosine laws to solve problems.