This self checking worksheet contains 4 triangles at the top of the page. The student must first find the missing side of each triangle. (Two of the four triangles use a radical.) Then, eleven sum or difference problems are listed. There are 4 sine, 4 cosine and 3 tangent problems for the students to complete. This is a good assignment review before a test. When complete, the students will discover the authors to two books which have never been written.