Geometryhard · Past Paper
In triangle ABC, side b = 20, c = 21 and sin A = 3/5. Find side a.
A13
B29
C17
D25
✓ Correct Answer: A — 13
cos A = 4/5 (assuming A is acute). a^2 = b^2 + c^2 - 2bc cos A = 400 + 441 - 2(20)(21)(4/5) = 841 - 672 = 169. a = 13.
Share this question
More from Geometry
- If the circumference of a circle is equal to the perimeter of a square, then the ratio of their areas is:
- Find the value of k if the point (k, 3) lies on the line 2x + 3y = 11.
- What is the x-intercept of the line 2x + 3y = 6?
- The coordinates of the origin are:
- If the slope of line AB is undefined, then line AB is: