diff --git a/guide/english/mathematics/area-of-a-triangle/index.md b/guide/english/mathematics/area-of-a-triangle/index.md
index 0c8d40a819..300943aa01 100644
--- a/guide/english/mathematics/area-of-a-triangle/index.md
+++ b/guide/english/mathematics/area-of-a-triangle/index.md
@@ -57,7 +57,7 @@ Sin - The sine trigonometric expression.
    
 2. If two sides of a triangle are known to be 3 and 6, and the angle between them is 30 degrees, what is the angle of the triangle?
 
-   Area = 0.5 x 3 x 6 x sin(30 degrees) = 4.5 units<sup>2</sup>
+   Area = 0.5 x 3 x 6 x sin 30° = 4.5 units<sup>2</sup>
 
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