maths homework, please help?

Question

The lenghts of the sides of a triangle are 4.2cm, 5.3cm and 7.6cm.

Q1. Calculate the size of the largest angle of the triangle.

Answer 1

Hey , I recently taught my students this...

Try using the Law of Cosines... Here is a link to the article on Wikipedia. They have a pretty good explanation for you.

http://en.wikipedia.org/wiki/Law_of_cosines

Answer 2

First, you should realise that the biggest angle is opposite the biggest size.

[NB. take note of upper and lower cases when labelling]
Make a rough sketch of how the triangle may appear, as it is not particularly important to draw it accurately. Now label the biggest angle vertex "C", the biggest side (which is opposite the biggest angle) "c", either of the other two sides "a", the angle opposite "A", and the final length "b" and the final angle "B"

Use this formula: c^2 = a^2 + b^2 - (2)(a)(b)(cosC)
[Note also that ^2 means squared]
Its the Cosine Rule by the way

Answer 3

http://www.teacherschoice.com.au/Maths_Library/Trigonometry/triangle_given_3_points.htm

The link above will take you to a page that will walk you through finding the largest angle of the triangle (and other things). The part you want is about half-way down the page -
Step 1 - Begin by using the cosine rule to find the largest angle.

Good Luck!

Jen

Answer 4

draw the triangle and then use a protracter ask ?z that you need help with not that you are too lazy

btw it will be a scalene so one angle is obtuse